It is a great happiness to be with you today, and I am deeply honoured to be delivering the Lionel Cohen Lecture. That we should come together at the Hebrew University in Jerusalem, which I have had the great pleasure to visit on several occasions, stretching back many years, adds to the sense of personal significance.

We come together today as a group, yet each of us is also an individual, and my theme today is the relationship between the two. I have come to understand that my various activities – teaching, writing, litigating – are informed by matters of background, by baggage attached to me as I entered this world. I was not a blank slate; indeed none of us are. The point was recognised by historian Eric Hobsbawm, in his fine autobiography Interesting Times.Footnote ¹ He wrote of the connection between who we are and what we do, the ‘profound way in which the interweaving of one person's life and times, and the observation of both, [help] to shape a historical analysis’.Footnote ² I am not a historian but a lawyer, who focuses on matters international. My professional and academic interest is a desire to understand how the law functions: how rules come into being; how they are interpreted and applied; how they affect behaviour, of individuals and groups, of corporations and states. My curiosity about a person's life and times concerns the way it might inform the world, and the experiences of the past quarter of a century in my work – not least in the courtroom, appearing before international judges from different backgrounds – point to a rather clear conclusion: individual lives and personal histories matter, and they can make a difference.

My book – East West Street: On the Origins of Genocide and Crimes against Humanity Footnote ³ – was seven years in the writing. It is not about the life of one person, but four. It seeks to understand how the particular circumstances of each contributed to the roads he took, and how different roads individually travelled changed the system of international law that is my daily work.

The book also touches a more personal theme: how four interweaving lives influenced my path, directly and indirectly. That path raises questions that touch each of us, addressing central matters of identity. Who am I? How do I wish to be defined – as an individual, or as a member of one or more groups? How do I want the law to protect me – as an individual, or as a member of a group? Such questions are as pertinent today as they were when the legal concepts of ‘crimes against humanity’ and ‘genocide’ were coined, back in the summer of 1945.

East West Street came about by chance, like so much in life. It was the spring of 2010; I was immersed in the classrooms of UCL, in academic articles, in cases in The Hague. An invitation arrived from Ukraine, an email from the Law Faculty of the University of Lviv – the city known as Lemberg during the Austro-Hungarian empire until 1918, then Lwów during the Polish years until 1939, then Lviv after 1945. Would you visit and deliver a public lecture on your work on ‘crimes against humanity’ and ‘genocide’, the email inquired, about the cases in which you have been involved, about your academic work on the Nuremberg trial, about the trial's consequences for our modern world?

Yes, I replied, I would. I had long been fascinated by the trial and the myths of Nuremberg, by the words, images, sounds. The trial was catalytic: a moment when our modern system of international justice crystallised into being. I was mesmerised by odd points of detail to be found in the lengthy transcripts and by the grim evidence; drawn to the books and memoirs and diaries that described in forensic detail the testimony that was laid before the judges, the love affairs that went on behind the scenes. I was drawn to movies like Judgment at Nuremberg, the 1961 Oscar winner made memorable by Spencer Tracy's momentary, unexpected flirtation with Marlene Dietrich and the line from his closing judgment: ‘We stand for truth, justice and the value of a single human life’. There was, too, a practical reason for my interest, because the trial's influence on my work had been profound: the Nuremberg judgment blew a powerful wind into the sails of a germinal human rights movement. Yes, there was a strong whiff of ‘victor's justice’, yet the case was catalytic, opening the possibility that the leaders of a country could be put on trial before an international court. That had never happened before.

It was probably my work as a barrister, rather than my writings, that caused the invitation to be sent from Lviv. In the summer of 1998 I was involved in the negotiations in Rome that led to the creation of the International Criminal Court (ICC), a body with jurisdiction over ‘genocide’, ‘crimes against humanity’ and two other international crimes. The essential difference between the two concepts is on who is protected, and why. Assume thousands of people are killed, murdered, exterminated. The systematic killing of such large numbers of individuals will always be a ‘crime against humanity’, but will it be a ‘genocide’? That depends on the intent of the killers and the ability to prove motive. To establish the crime of ‘genocide’ it is necessary to show that the act of killing is motivated by a special intent: to destroy a group in whole or in part. If a criminal prosecutor cannot prove that a large number of people have been killed with that intent, then in law the crime of ‘genocide’ is not established. So you have the two concepts operating side by side, and overlapping: every ‘genocide’ is also a ‘crime against humanity’, but not every ‘crime against humanity’ is a ‘genocide’.

A few months after both crimes were inscribed into the Statute of the ICC,Footnote ⁴ Senator Pinochet was arrested in London on charges of ‘genocide’ and ‘crimes against humanity’ laid by a Spanish prosecutor. The House of Lords ruled that even as a former president of Chile he was not entitled to claim immunity from the English courts. That was a novel, revolutionary judgment.Footnote ⁵

In the years that followed, the gates of international justice creaked open, following five decades of relative quiescence during the Cold War chill that came after the Nuremberg trial. The trial of EichmannFootnote ⁶ in Jerusalem was, of course, a trial before a domestic court, not an international trial.

Cases from the former Yugoslavia and Rwanda landed on my desk in London. Others followed, relating to allegations in the Congo, Libya, Afghanistan, Chechnya, Iran, Syria and Lebanon, Sierra Leone, Guantánamo and Iraq, as well as Israel and Palestine. These were based on the new rules that came into being after 1945 – a revolutionary moment in the making of modern international law, one that recognised that the rights of the sovereign over its people were no longer unlimited. The long and sad list of cases that reached me reflected the failure of good intentions aired in Courtroom 600 of Nuremberg's Palace of Justice. I became involved in too many cases that concerned mass killings. Some concerned crimes against humanity, the killing of individuals on a large scale; others focused on genocide, the destruction of groups.

The two distinct crimes, with different emphases on the individual and the group, grew side by side, although over time genocide seems to have emerged, in the eyes of many, as the ‘crime of crimes’. The supposed hierarchy leaves an unfortunate suggestion that the killing of large numbers of people as individuals is somehow less terrible. Occasionally, I picked up hints about the origins of the two terms, and the connection with arguments first made in Courtroom 600, but I never really inquired about what exactly had happened in Nuremberg. I knew generally how the new crimes came into being and how they subsequently developed, but little about the personal stories behind them. The invitation from Lviv offered a chance to explore.

I could tell you that I went to Lviv to give a lecture, but that would not be true. I went for another reason – my grandfather, who was born there in 1904. Leon Buchholz called it Lemberg when he spoke in German, Lwów in Polish. In his wonderful slim volume Moy Lwow, written in 1946 (recently published in English by Pushkin Press as City of Lions Footnote ⁷), the Polish poet Jòzef Wittlin describes the ‘essence of being a Lvovian’. ‘An extraordinary mixture of nobility and roguery, wisdom and imbecility, poetry and vulgarity’, he wrote, but added that ‘[n]ostalgia … likes to falsify flavours … telling us to taste nothing but the sweetness of Lwów today’. ‘I know people’, he continued, ‘for whom Lwów was a cup of gall’.

So it was for my grandfather, a cup of gall buried deep, a hidden hinterland of which he never spoke to me or my brother. Leon's silence barely covered the wounds of a large family he left behind in 1914 when he moved to Vienna, then lost forever after 1939 when he was expelled and went to Paris. Yet the moment I first set foot in Lviv, in the autumn of 2010, it felt familiar, like an encounter with a long-lost relative. That dark city was part of my DNA; I missed it, and I felt comfortable there.

What caused that reaction made me explore various writings on the special relationship between grandparent and grandchild. I was directed to the work of Maria Torok and Nicolas Abraham, two Hungarian psychoanalysts. ‘What haunts are … the gaps left within us by the secrets of others’,Footnote ⁸ they wrote, the words with which I open East West Street. Leon's secret was that he came from a huge family, centred in Lemberg and the environs, with dozens of uncles, aunts, cousins, nephews and distant relatives. The family grew until 1939, when war came again to the city. Within six years, by the spring of 1945, Leon was the last of more than eighty members of that family still alive, the only survivor – or so I thought – from Galicia. Amongst the papers I saw for the first time as I prepared for the trip to Lviv I found the expulsion order. Translated into English it says: ‘The Jew Buchholz Maurice Leon is required to leave the territory of the German Reich by December 25, 1938’. He could be expelled because he had been made stateless. That is one reason, no doubt, I feel so strongly about the current fad in some countries, including the UK, to strip certain people of their nationality. One thing leads to another, always.

I had always assumed Leon had left Vienna with his wife Rita, my grandmother, and his one-year-old daughter Ruth, my mother. Now I learned this was not the case, and it was this central fact, I think, which lay deep and which touched my family and my childhood.

Leon left Vienna and made his way alone to Paris. Thus did I learn that his daughter travelled to Paris a few months later, and that his wife remained in Vienna for three more years. Something else must have intervened in their lives before the three separated in January 1939.

• • Why did Leon leave Vienna on his own?

• • How did my mother Ruth get to Paris alone, as an infant of less than a year?

• • Why did Rita remain in Vienna, allowing herself to be separated from her only child?

These and other questions were big, and they hung in the air, as such questions will. I returned to the documents found amongst Leon's papers, looking for clues. As a litigator – a sort of lesser, amateur historian-cum-psychiatrist– you learn that every scrap of paper or photograph is capable of hiding information that may not be immediately knowable. This is the muck of evidence that I have come to love. Look carefully, keep an open mind, attend to the unexpected, find the dots, try to join them, persist. Nothing is ever only what it seems.

Two items stood out.

The first was a tiny scrap of thin yellow paper, folded in half, one side blank, the other with a name and address written firmly in pencil. The writing was angular and strong. ‘Miss E.M. Tilney, Norwich, Angleterre’. The second item was a small black-and-white photograph, taken in 1949, not quite square. It showed a middle-aged man staring intently into the camera, a faint smile across the lips, a pin-striped suit, a neatly folded white handkerchief, a polka-dot bow tie that suggested a slightly mischievous air. On the back of the photograph, in blue ink, was written: ‘Herzlichste Grüsse aus Wien, September 1949’ (‘Warmest wishes from Vienna’). There was a signature, the writing firm but indecipherable.

My mother told me she did not know who Miss Tilney was, or the identity of the man in the bow tie. I didn't believe her. I pinned the scraps on the wall above my desk – where they would remain for three years, in the hope they might shed light on what had happened to my grandfather in 1939 – and I turned to write the lecture for Lviv.

* * *

I have taken you off on a personal detour, so let us return to ‘crimes against humanity’ and ‘genocide’, and the first of several ‘coincidences’ I encountered. In preparing the lecture I was surprised to discover that the man who put ‘crimes against humanity’ into international law came from Lviv. Indeed, he was a student at its university, although those who invited me were blissfully unaware of the fact.

His name was Hersch Lauterpacht. He was born in the small town of Zolkiew, about 15 miles north of Lviv, and moved to Lemberg in 1911 when he was 14, enrolling at the University law faculty four years later. In 1919 he moved to Vienna, where he spent four years studying with Hans Kelsen. He came to London in 1923, with his new wife, to study, then became a renowned academic, first at the London School of Economics, then at Cambridge. In 1945 he published a book that laid a foundation for the modern system of human rights. Titled An International Bill of the Rights of Man,Footnote ⁹ it offered a revolutionary idea: to recognise that every human being on the planet has rights as an individual under international law, something that did not then exist. He prepared 20 draft articles, which covered much that was new but was by no means exhaustive. Notable omissions included torture and discrimination against women, and realpolitik informed his approach to the situation of non-whites in South Africa and what he called ‘the thorny problem of actual disenfranchisement of large sections of the Negro population in some States of the United States’. Yet the draft Bill gave effect to his credo that ‘[t]he individual human being … is the ultimate unit of all law’.

In April 1945, after the war in Europe ended, Churchill, Roosevelt and Stalin agreed on a criminal trial for senior Nazi leaders. The British hired Lauterpacht to assist in the prosecution, to work with Robert Jackson, the US chief prosecutor. In July 1945 Jackson travelled to London to draft the Charter of the Nuremberg Tribunal. The four powers – America, Britain, France and the Soviet Union – disagreed about the crimes over which the Tribunal would exercise jurisdiction. Jackson turned to Lauterpacht for help. On 29 July, Jackson was driven from Claridge's Hotel in Mayfair to the Lauterpachts’ garden in Cambridge, at No 6 Cranmer Road. They sat in the garden, had tea and cakes, discussed the problem of the list of crimes. Lauterpacht suggested the idea of inserting titles in order to help public understanding and add legitimacy. Jackson reacted positively. Lauterpacht offered another idea, on atrocities committed against civilians, a matter on which the Soviets and Americans were deeply divided. Lauterpacht's interest was academic, but also personal: he had no news about his family in Lemberg, a matter of which, as an emerging Englishman, he said nothing to Jackson.

Why not refer to the atrocities against civilians as ‘crimes against humanity’, Lauterpacht suggested. Here we see the words in his own hand. The term would cover atrocities against individuals on a large scale – torture, murder, disappearance – and introduce the new concept into international law. No legal instrument had ever used the term. Jackson liked the idea, took it back to London and a few days later, on 8 August, ‘Crimes against Humanity’ was incorporated into the Nuremberg Charter, as Article 6(c) of the Statute.Footnote ¹⁰ ‘[C]learly an innovation’, Lauterpacht told the Foreign Office in London, but one that was necessary to signify that those who break international law ‘cannot shield themselves behind the law of their State’.

* * *

Preparing the Lviv lecture required me to focus also on ‘genocide’, and this brings me to a second surprise: the man who invented that word – in 1944 – also passed through Lviv and studied at the same law school. His name was Rafael Lemkin. He started at Lwów University in 1921, two years after Lauterpacht left, and in 1926 obtained his doctorate in criminal law. Those who invited me to Lviv were unaware too of his connection with the university.

After law school he became a public prosecutor in Warsaw. In 1933 he wrote a paper for a League of Nations meeting in Madrid, proposing new international crimes to combat ‘barbarity’ and ‘vandalism’ against people. His focus was not on the protection of individuals, like Lauterpacht, but on the protection of groups, sometimes referred to as ‘minorities’. His ideas bounced around, but nothing came of them as Hitler had just taken power in Germany.

In 1939, when Germany invaded Poland, Lemkin was in Warsaw. He escaped to Sweden, via his parents’ town of Wolkowysk, which was under Soviet control. In 1941 he travelled to America, on the long route – across Russia, to Japan, by boat to Seattle, then train to Durham, North Carolina, where he was offered a place of academic refuge at Duke University.

He travelled with little money and almost no personal belongings, yet there was a great deal of luggage, trunks filled with paper, thousands of pages of decrees promulgated by the Nazis across occupied Europe, which he had gathered and now carted around the world. In America he analysed the decrees and was given a contract to write a book to describe the patterns of behaviour, the indicia of an underlying master plan, not made explicit. The book was published in November 1944, with the title Axis Rule of Occupied Europe.Footnote ¹¹ Chapter IX was entitled ‘Genocide’. Lemkin had invented a new word: the crime of the destruction of groups, the Nazi master plan, an amalgam of the Greek word genos (tribe or race) and the Latin word cide (killing). Here you see it in his hand.

In the summer of 1945, Lemkin was hired by the US government to work on war crimes, and began to work with Robert Jackson and his team, separately from Lauterpacht. He pushed his idea of genocide, a crime for which he wanted the senior Nazis to be indicted. In his view, the destruction of groups, the greatest of crimes, was a matter for the Nuremberg Tribunal.

In August 1945, when the Nuremberg Charter was adopted following Jackson's visit to Lauterpacht in Cambridge, Lemkin was greatly disappointed that it included ‘Crimes against Humanity’ – the killing of individuals – but made no mention of genocide, and was silent about the destruction of groups.

Lemkin did not give up. He flew to London, where the Indictment for the defendants was being crafted. He pressed actively for ‘genocide’ to be included – a ‘persistent bugger’, Jackson's son wrote to his mother – but there was strong opposition to ‘genocide’ in Jackson's office, under pressure from Southern senators concerned about discrimination against African-Americans, and from the British, concerned about the colonial legacy.

Nevertheless, against the odds, Lemkin's word made it into the draft Indictment. Genocide was included in Count Three, as a ‘War Crime’, to include the murder of civilians in occupied territories, including Lemberg and Wolkowysk, where his parents lived (like Lauterpacht, he had no news of his family's fate). The Indictment alleged that the Nazis ‘conducted deliberate and systematic genocide,’ the first time the word was used in an international legal instrument, with an agreed definition: the ‘extermination of racial and religious groups’. The Indictment mentioned ‘Jews, Poles, Gypsies and others’.Footnote ¹²

On 18 October the Indictment was filed at the Tribunal. ‘I went to London and succeeded in having inscribed the charge of Genocide against the Nazi war criminals in Nuremberg’, Lemkin would claim.

* * *

The Nuremberg trial opened on 20 November 1945. Lauterpacht was present in the courtroom, with the British team, pushing for the protection of individuals. Lemkin was back in Washington, with the American team, pushing for the protection of groups.

One of the 22 men in the dock was Hans Frank, the fourth character in East West Street. He too was a lawyer, and from the late 1920s served as Adolf Hitler's personal lawyer. In 1933 he became Bavarian Minister of Justice and in October 1939 he became Governor General of Nazi-occupied Poland. On 1 August 1942 he visited Lemberg and Galicia, recently incorporated into his territory. He hosted a concert, which finished with Beethoven's Ninth Symphony, and gave a speech in the very room in which I would lecture seven decades later – the Aula of the University – to announce the elimination of the city's entire Jewish population. Amongst those caught up in the horrors in the days that followed were the families, friends and teachers of Lauterpacht and Lemkin, as well as my grandfather's family. For each family there would be only a single survivor.

Frank did not seem unduly perturbed by the actions he had unleashed, but rather more bothered by other mundanities. He lodged at the home of his deputy, Otto von Wächter, Governor of Galicia, the principle character in the BBC radio and podcast series I have recently made, The Ratline (which will be published in April 2020 with that title, the sequel to East West Street). Frau von Wächter recorded in her diary that she played chess with Frank that day. After she won twice, he ‘angrily went to bed’.

In May 1945 Frank was caught by the US Army near his home in Bavaria. With him were his diaries – 42 volumes – and a remarkable collection of artworks, including the portrait of Cecilia Gallerani, painted by Leonardo da Vinci in about 1489. It hung in Frank's private office in the Wawel Castle in Krakow, where it hangs again today. Frank's son Niklas, who I have come to know, tells me that as a young boy his father made him stand before the painting and slick down his hair, like Cecilia, and the little boy was frightened of the animal, which he thought was a rat. It is, of course, The Lady with an Ermine. Now Frank was in the dock, charged on three counts, including ‘Crimes against Humanity’ and ‘Genocide’.

On the first day of the trial, the Soviet prosecutors took the judges to the events in Lviv following Frank's visit. They described acts of murder and torture and other ill-treatment as ‘genocide’. More than 130,000 people were killed during that period, including eight thousand children murdered in just two months in the Janovska camp, at the heart of the city. As the words are being spoken in Courtroom 600, Lauterpacht and Lemkin do not know whether the victims include their families. They are not aware that the man they are prosecuting, Hans Frank, was directly implicated in the murder of their own families.

On this day, for the first time ever, the terms ‘genocide’ and ‘crimes against humanity’ were used in open court. I knew Lauterpacht and Frank to be in the same room on this day, and I wonder if there is a photograph. Lauterpacht's son told me there is none but, as with my mother, I didn't believe him. In the archive of Getty Images, I spent a long day going through hundreds of old glass-plate images, each to be taken out of its protective paper sleeve. Finally, after several hours, I find this: there is Lauterpacht, at the end of the British table, the second on the left, elbows on the table, hands clenched under the chin. He is attentive, behind the counsel's lectern at which a Soviet prosecutor speaks. In the lower right-hand corner you can see the large figure of Goering, in an oversized light-coloured suit. Moving along the bench to his left, six along and just before the image was cut by the protruding balcony, is the semi-bowed head of Frank.

Divided by no more than a few tables and chairs, Lauterpacht and Frank are together in the same room.

* * *

The trial lasted for a full year, and judgment was handed down over two days, on 30 September and 1 October 1946. I do not have time to reveal what transpired over the course of that remarkable year, as the lives of our three characters became increasingly intertwined. Suffice it to say that the connections were unexpected: a series of happenings which the historian Antony Beevor described as being of a kind that ‘no novel could possibly match’. The point I make is that those personal journeys coincided in ways that produced an outcome to change the course of legal history, and then history itself. The ideas and endeavours of Lauterpacht and Lemkin have influenced politics, history, culture, my life and yours.

The concepts of ‘crimes against humanity’ and ‘genocide’ have entered our world, although many are under the impression that they have existed since time immemorial. They have not: both legal concepts are the product of creative and inventive minds, two men driven by their own experiences, forged on the anvil of a single city. Why Lauterpacht opted for the protection of the individual, and what caused Lemkin to embrace the protection of the group, is a matter of speculation. Their backgrounds were similar: two Polish Jews who studied at the same university with the same teachers. If you want to trace the origins of these crimes, you can trace them to Lemberg, to events at the end of the Great War, to the law faculty. Indeed, you can trace the origins to one teacher they both had – Julius Makarewicz, a renowned Polish professor of criminal law. You can follow the line to a building, and to the very room where Makarewicz shared his ideas on the treatment of minorities, which I found.

Something else also strikes me as remarkable: despite their common origins, interests and journeys, and the fact that I have located Lauterpacht and Lemkin in the same city on the same day – although not in Nuremberg or Courtroom 600, where they missed each other, sometimes by only a day – it seems that the two never actually met.

The concepts they put into international law – ‘crimes against humanity’ and ‘genocide’ – inform my working life. I have frequently wondered how it could be that I ended up doing the work I do. My quest to understand Lauterpacht and Lemkin was surely driven by my personal history, and by stories that had been buried away in family crypts, no doubt for protective reasons.

The quest led to more family detective work. I did learn who Miss Tilney was and what she did, and now understand why my mother – and I, and my brother – have reason to be deeply grateful to a remarkable and courageous woman who did missionary work on behalf of the Surrey Chapel in Norwich into which she was born, motivated by the sermons of her pastor, David Panton, and Chapter 10, verse 1 of Paul's Letter to the Romans. This single line, it seems, motivated her to travel to Vienna and save my mother's life in the summer of 1939. As a result of the research, Miss Tilney was honoured as a Righteous Among the Nations at Yad Vashem.

I also uncovered the identity of the man in the bow tie. The journey took me east then west, across rivers and an ocean, assisted by a pile of old Austrian telephone directories and a wonderful private detective in Vienna; finally Facebook cracked it, taking me to an attic in Massapequa, Long Island in New York. Here a photograph emerged to offer a key that unlocked another family mystery: an image caught in a garden in Vienna in the spring of 1941, my grandmother with two men in white socks, one being the man in the bow tie, her lover. That discovery catalysed another: the identity of the man who may have been my grandfather's true love, his best friend Max.

Such efforts took years, and involved the assistance of a range of remarkable individuals. These are the requirements for an exercise in personal archaeology. Even more remarkably, and unexpectedly, I came to learn of the more direct connections between my family and the Lauterpachts and the Lemkins. I discovered that my great-grandmother, Amalia Buchholz (nee Flaschner), was born and lived in the small town of Zolkiew, where Hersch Lauterpacht was born. It gets better: they were born and lived on the same street, Lembergersterstrasse, just a few hundred yards apart. Coincidentally, or perhaps not, Lauterpacht's son and only child, Eli, was my first teacher of international law in 1982, and later my mentor. For more than three decades we worked – at the university and at the bar – but it was only in 2014 that we learned of the shared connection with the street that writer Joseph Roth referred to as East West Street.

I learned that Amalia's life, which began on the street of the Lauterpachts, ended in September 1942 in the kingdom of Hans Frank. The last street down which she walked was Himmelfahrtstrasse, the ‘street to heaven’, which led from a railway platform to a gas chamber at Treblinka. A month later Lemkin's parents, Bella and Josef, walked down the same street, and died in the same gas chamber.

Amalia's life was caught between the Lauterpachts and the Lemkins. It could be said that mine is, although in a rather different way.

* * *

How does one begin to understand these points of connection?

The starting point is marked by the ideas of these two remarkable men, Lauterpacht and Lemkin, and the enduring relevance of their ideas today. The relationship between the individual and the group has been contested across the ages. I was reminded of this when I came across a letter written by Lauterpacht to his son Eli, as he was preparing a draft of the closing arguments to be delivered at Nuremberg by Sir Hartley Shawcross in July 1946. Having recently learned that all but one member of his Lemberg family had been murdered – on the orders of Hans Frank, whom he was prosecuting – it must have been a time of intense anguish, of personal grief and professional challenge. To his son, he explained that he managed to find solace and strength in the strains of Johann Sebastian Bach's St Matthew Passion. Remarkably, at that same moment, in the summer of 1946, Hans Frank told the US Army psychologist attending to him, Dr Gustave Gilbert, that in these most trying of times, as the trial reached its climax, he took refuge in the imagined listening to the same piece of music – the St Matthew Passion.

How remarkable that two men, on opposite sides of the same courtroom, might find solace in the same piece of music. I have come to understand the work's resonance for Lauterpacht, who was fluent in German: the libretto reflected Bach's emphasis of the Pietist belief in the individual, with every aria but one being sung as ich – I – and the three landmark choruses sung in the first person plural. In this way Bach signalled the bypassing of the priest-celebrant and the church, the group, allowing the individual a direct connection with God. For Frank, with his scathing disregard for the integrity of the individual, the connection is more difficult to understand, not least given the work's scathing attack on the Catholic faith to which he had converted just a year earlier, following a failed suicide attempt.

Lauterpacht believed that we should concentrate on the protection of the individual, and would surely argue, even today, that Lemkin's invention of the concept of ‘genocide’ has been practically useless and politically dangerous; that it will tend to replace the tyranny of the state with the tyranny of the group. In a way, my own practical experience concords with that view, having observed that the focus on the protection of one group against another tends to reinforce the sense of ‘them’ and ‘us’, to amplify the power of group identity and association, a source both of sustenance and danger.

How does this happen? In seeking to prove that a ‘genocide’ has occurred, in law you have to establish the existence and expression of an intent to destroy a group in whole or in part. I have seen for myself how that process reinforces a sense of victimhood in the targeted group, and hatred towards the perpetrators as a mass.

Yet I also understand what Lemkin was trying to do. He was surely right to recognise a reality, that in most (if not all) cases mass atrocity is targeted not against individuals but against those who happen to be members of a group. Lemkin would say, and it is a powerful argument, that the law must reflect that reality, to recognise and give legitimacy to a feeling we all have, of association with one or more groups.

This profoundly strong sentiment was brought home to me very recently while writing an article for the Financial Times magazine: a profile of Dr Jan Kizilhan, the German psychologist who has established a programme to assist the Yazidi women and girls who were enslaved, tortured and raped by individuals associated with ISIS, bringing 1,100 of them to Germany for medical and psychological treatment.Footnote ¹³ In his work, Dr Kizilhan identifies a connection between the possibility of justice and the future wellbeing of victims. ‘Calling it a genocide’, Dr Kizilhan told me, ‘recognises the group's identity, what is being done to it, and its right to exist’. In this way, the implication is that ‘crimes against humanity’ is not enough.

Nevertheless, I am concerned about the hierarchy that seems to have emerged, one that puts ‘genocide’ atop the list of horrors, so that a mere ‘crime against humanity’ or ‘war crime’ is seen somehow as a lesser evil. Call something a genocide and it will be on page 1; call it a crime against humanity and it will only be on page 13. That is the power of the word invented by Rafael Lemkin, and perhaps too of our association with the protection of the group.

What, one might ask, is the enduring legacy of these two legal terms? The crime of genocide, and the idea that each of us as individuals has rights under international law, were new in 1945. The moment of creation was significant, revolutionary even, a recognition that sovereignty over human beings is not unlimited. Yet the crimes continue.

Today, once more, the poison of xenophobia and nationalism is coursing its way through the veins of Europe, and many other parts of the world. The strong leader is back. I see it on journeys to the central and eastern parts of our European continent. I see it in making the BBC documentary My Nazi Legacy, on my relationship with the sons of Hans Frank and Otto Wächter. I see it in making The Ratline podcast, on the fugitive flight and strange death of Otto Wächter, in the Vatican, travelling across Europe, in Austria, in Viktor Orban's Hungary, in Poland. Here and in other places it is hard to avoid what is stirring, and to wonder to where such stirrings will lead.

The generation that experienced the horrors of the 1930s, that lived through the Second World War, that knows why states came together after 1945 to create a United Nations, to embrace multilateral cooperation and the idea of an international rule of law, to adopt in the Palais de Chaillot in Paris in December 1948 a Universal Declaration of Human Rights and a Convention on the Prevention of Genocide, that generation will soon be gone. Perhaps the disappearance of actual experience, of first-hand memory, allows our politicians to take for granted what occurred in 1945, and to forget.

It is impossible not to have gone through the experience of writing East West Street and the projects that have followed, an immersion in the world of the years between 1914 and 1945, and not feel an acute sense of anxiety as to what is stirring.

Two years ago the man who is now President of the United States, a devotee of lawlessness in this region, called ‘for a total and complete shutdown for Muslims entering the United States’. The idea of targeting people not because of their individual propensities but because they happen to be a member of a particular group has a long, dark history. The idea of a travel ban based on a person's nationality, or religion, or race, is deeply troubling. Experience teaches us to where such a beginning can lead, singling out people not for what they might have done but because they happen to be a member of a particular group. One thing leads to another.

In Britain, too, change is in the air, a move to identity politics, an embrace of antisemitism and islamaphobia. Two years ago the Prime Minister – who indicated she would take the United Kingdom out of the European Convention on Human Rights if she could, but who (at the time of writing) it seems is unable even to deliver Brexit – told her party conference that ‘[i]f you believe you are a citizen of the world, you are a citizen of nowhere’.

Her words reminded me of a passage in Stefan Zweig's magnificent book The World of Yesterday Footnote ¹⁴ – required reading for our times – published posthumously in 1942, after Zweig committed suicide. ‘For almost half a century’, he wrote, ‘I trained my heart to beat as the heart of a citizen of the world. On the day I lost my Austrian passport I discovered that when you lose your native land you are losing more than a patch of territory within set borders’.

One thing leads to another. One former London Mayor offensively evoked Adolf Hitler as a supporter of Zionism. Another former London Mayor – who, shockingly, later served as Foreign Secretary – suggested that the European Union and Adolf Hitler somehow share common aims. Brexit and Trump are surely a reflection of a new direction.

And, of course, Israel is hardly untouched by matters of identity, by conceptions of the individual and the group.

From a distance, what one hears and reads is perplexing. Last summer the Prime Minister of Hungary raged against ‘an enemy that is different from us’, an enemy that is ‘[n]ot open, but hiding; not straightforward but crafty; not honest but base; not national but international; does not believe in working but speculates with money; does not have its own homeland but feels it owns the whole world’.Footnote ¹⁵

To which individual or group might he be referring? George Soros certainly, but not only him. A few weeks later the Prime Minister of Israel welcomed the same Prime Minister of Hungary, peddler of antisemitic tropes, to this country as ‘a true friend of Israel’.Footnote ¹⁶ He did so on the day the Knesset adopted a Basic Law on Israel – The Nation State of the Jewish People, which declares that ‘[t]he state of Israel is the nation-state of the Jewish people’, and retained a conspicuous silence on the matter of equality and equal rights for all citizens. Questions have been raised – understandably – as to whether the intention and effect of the new Law is to undermine rulings of the Supreme Court to the effect that a citizen of Israel will not have more rights merely because she or he is Jewish, or that a member of another group, for that reason alone, will have fewer rights.Footnote ¹⁷ Concerns are hardly put to rest when the Prime Minister of Israel, in response to a comment by the actor Rotem Sela and citing the new Basic Law, states that Israel ‘is not a country of all its citizens’.Footnote ¹⁸

The words sound darkly familiar to the author of East West Street, steeped in the cities of Lviv, Vienna and Berlin. In Italy, too, the writer Primo Levi knew something about hierarchies amongst the citizenry, and to where that leads, and all the more so when he arrived in Auschwitz. I invite you to read the Preface to his book If This Is a Man,Footnote ¹⁹ published in 1947 (but not available in Hebrew until 1989, after he died). Primo Levi wrote:

When this happens, he continued:

This is the context – past and present, unspoken dogmas, the stranger, them and us – in which I oscillate between the views of Lauterpacht and Lemkin, between the individual and the group, between the realism of Lemkin and the idealism of Lauterpacht. I can see the force of both arguments, and recognise the tension and the struggle between the individual and the group, between crimes against humanity and genocide, one that will not soon be resolved. International law today embraces both.

We are at a dangerous moment. Our politicians seem not to be able to recognise how precious was the settlement of 1945, and how vulnerable is the acquis that was created, one that has offered a foundation to international relations in our time. We cannot take for granted what was achieved back then.

This is the context – past and present – in which I ended East West Street, at a long ago site of mass killing, caught between my head and my heart, intellect and instinct, recognising the need to value the inherent worth of every human being, yet understanding too the pull of tribal loyalty, the essential truth of the notion that we are indeed haunted by ‘the gaps left within us by the secrets of others’, and the possibility that the discovery of such a haunting will not necessarily destroy us but may actually make us stronger.