When he contemplated the writing of an autobiography towards the end of his life George Bell found that he was unsure whether it should be written as an ecumenical or an Anglican narrative. The Presbyterian Kenneth Slack, to whom he expressed his dilemma, urged that it must surely be the latter. Yet Bell's reflection strikes a chord. Where did his essential contribution lie, after all? He was too much the internationalist to be the predictable English bishop, too much involved in politics to be wholly the conventional ecclesiastic, and too much a Christian for other Churches to be quite recognisable as the property of one. In history Bell has fallen not into that far greater picture to which we might have turned but merely out of our range, almost altogether. The inexorable deepening by historians of national and denominational perspectives has made the ecumenical enterprises that once flourished, and made the boldest claims, strangely obscure. It would be wholly right to view these volumes as a contribution to ecumenical history. But then can such a thing now be said to exist in any organised, coherent form?

Bell and Visser ’t Hooft were certainly colossi of the years which marked the high tide-mark of ecumenical ambition, and they bestrode the committee rooms and conferences which were characteristic of the ecumenical movement with a marvellous, constructive intent. It could be said that they had come to represent the creative arguments and possibilities of a liberal establishment visible across most European and North American Protestant Churches in the middle twentieth century. Both were, in a sense, the heirs of Archbishop Söderblom; Bell had risen through a national Church which looked to a wider world while Visser ’t Hooft had risen to prominence through the international student Christian movement. They had both been patrons of friends in Germany who had resisted Hitler; both were convinced Europeans who looked to a new age of international organisations to provide the creative guarantees of peace between nations. In short, they inhabited the same world, often knew the same people, and understood each other intuitively as allies. In many diverse moral and practical ways they even came to depend on each other.

The work of the eminent German historian Gerhard Besier has over many years come to represent a fundamental contribution to twentieth-century church history. He has done well to publish this collection in Britain. The letters themselves are to be found in two great collections, in Lambeth Palace Library in London and at the World Council of Churches in Geneva. Besier's introduction is almost entirely the article which he published in an earlier collection of international essays on Bell, in 2012. The material which follows is certainly considerable: here, altogether, are 1,431 letters and associated documents. Many are substantial and rich in content. A small but significant proportion represents, if briefly, other participants in the great drama, like the indefatigable British Presbyterian William Paton, the persevering French ecumenist H. L. Henriod, the difficult German Lutheran Bishop August Marahrens and the roving American Lutheran Stewart Herman. Even a brief glimpse at the index will offer proof of the still greater cast of international characters to which the letters and the associated papers point.

The rapport of the two correspondents is obvious: far from being stiff and official, the letters show an ease of style, a palpable honesty and a sharing of confidences which often makes them not only illuminating but engaging. The first volume shows the two men at work just before, during and after the volatile years of the Second World War, years which effectively drove their ecumenical enterprises in a number of revolutionary new directions, and often underground altogether. There turn out to be fewer letters here than might be expected: only three in 1943, a time when both men were deeply involved in maintaining their own connections with ‘the other’ Germany. The second volume is essentially defined by the early years of the WCC, the work of the Central Committee and the first general assemblies in Amsterdam in 1948 and Evanston in 1954; but the task of ecclesiastical empire-building also comes to involve purposeful attempts to draw the Churches of the Eastern Bloc and communist Asia into view, and successive entanglements in the troubles brought by the Cold War. All of this is handled with firm editorial competence: footnotes are copious throughout. It is not always clear how certain matters – appointments, initiatives, manoeuvres and appeals – find their place in a firm context that will be visible to the reader: a stronger supportive framework might have been welcome. The second volume concludes with the sermon which a failing Bell preached in Denmark shortly before his death, marking the tenth anniversary of the formation of the WCC, and then two eloquent tributes – one a fragment – written by Visser ’t Hooft afterwards.

To read the letters of these two very considerable figures is to uncover a realm of shared understandings and endeavours which would become, all too quickly and all too easily, a lost civilisation. Yet it was a civilisation which possessed courage, vitality and immense ambition. These two stout volumes represent a valuable contribution to ecumenical history, and it may be hoped that the very idea of such history will be fostered by them.