As he listened to the frantic voice on the phone, S. Rajaratnam realised that his greatest fear had come to pass. He tried not to give in to despair. It was difficult. As one of the chief architects of Singapore's independence, he had experienced some tough situations – but this was the worst tragedy to befall his country in his five years in politics.

It was 21 July 1964, barely a year after Singapore merged with Malaya and two Borneo states, Sabah and Sarawak, to form Malaysia in September 1963.

The voice on the phone that late afternoon was that of his close colleague Othman Wok, the social affairs minister. Othman had looked up to Raja, as the culture minister was usually known, since their journalism days in the 1950s. They had then worked for different newspapers – Raja was a famous columnist with the Singapore Standard, while Othman reported for the Malay-language newspaper Utusan Melayu – but both were joined in a common cause in the Singapore Union of Journalists to fight for social justice. Raja had led the union as its president with Othman as his deputy.

After Raja, together with Lee Kuan Yew and others, formed the People's Action Party (PAP) in 1954, Othman had joined the new left-wing party. What bound them was a common vision: to build a non-communal society based on justice and equality. In working towards this vision, Raja and Othman, as minority political leaders in a Chinese-dominated country, came to represent both the face and spirit of the party's multiracial ideology.

Now, on this hot, horrible day in July 1964, Othman bore news of a racial clash that threatened to tear apart the very fabric of society. “Some Malays are causing problems,” he reported. “Beating up Chinese bystanders. Things are getting out of control.”

Othman, the only Malay minister in the Singapore Cabinet, was leading a PAP contingent as part of a 20,000-strong procession to mark Prophet Muhammad's birthday that day.

Over the phone, he told Raja the scenes he had just witnessed: Malay youths punching a Chinese policeman struggling to control the rowdy procession as it headed towards the Malay settlement of Geylang, then breaking off from the march to attack Chinese passers-by at random. Sensing danger, he and several others had slipped into the People's Association headquarters in Kallang.