One had to admire his courage - not his wisdom. There sat Sir Nicholas Mosley trying, if not to defend, at least to explain the actions of his father, Sir Oswald, who in the 1930s terrorised the Jews of the East End. Sir Nicholas was addressing a meeting in the heart of the East End. His audience contained the Jewish veterans who had resisted Oswald Mosley and his Blackshirts 70 years ago, in what came to be known as the Battle of Cable Street.
The tone was wrong and the audience vented its anger as survivors bore witness to the real fear that Mosley and his Blackshirts brought to the East End.
For me it was a poignant occasion. As I listened to Mosley talking about where his father was 70 years ago, I thought about mine, who was literally on the other side of the barricades. And just as Mosley's father stayed "true" to his political ideology (fascism), so my father stayed true to his: communism. Mosley lived until 1980. My father died in 1956 - a momentously difficult year for communists. In February, Nikita Khrushchev revealed that Stalin was a psychopathic murderer. Later that year, Soviet tanks rolled into Hungary to crush the Budapest uprising.
My father was born in 1911 to parents who fled the anti-Jewish pogroms of tsarist Russia and found sanctuary in London's East End. Aged 12, he was sent to Germany to improve his Jewish education and wrote an account of his time there. It conjures up a picture of Germany as unthreatening, cosy. He returned to London to poverty, anti-Semitism and the growing threat of fascism. Like many other young Jews, he found himself attracted to the Communist Party. Jews were only 1 per cent of the population, yet made up 10 per cent of the party's members.
He was recruited into the party by a young woman who turned out to be secretary to Harry Pollitt, then leader of the British Communist Party. He collected subscriptions and eventually took charge of what the party called a "cell" - a group of local members. I still have clear memories of visiting them in north London and briefing them on the latest line to emerge from "King Street" - the party HQ.
He opposed the Second World War as "an imperialist plot against the Soviet Union". But when German troops invaded Russia, the USSR became our ally and my father - medically unfit to fight - took a job in an aircraft factory in support of the anti-imperialist struggle.
The end of the war brought the horrific realisation that the Nazis had murdered six million Jews. Some of his peers were looking to the creation of Israel as the way forward. There was also a growing recognition that the Soviet Union - an earlier promised land - was riddled with anti-Semitism.
By this time my father's political passion, undimmed spiritually, was undermined physically. He had cancer and, in 1956, was spending his last few months in hospital. He was hearing news filtered not through party HQ in King Street, but through the BBC. He was confused. What was happening to his world of certainties? "What are the comrades saying?" he would ask my mother, who couldn't help him: she had four kids to bring up.
The haemorrhaging of Communist Party membership was dramatic. From 1956-58 one in three party members left. Would my dad have stayed or left? He never had to make the decision - by the end of the year he was dead. But I think he would have stayed. I believe he would have echoed Sarah, the central character in Arnold Wesker's play of the time, Chicken Soup With Barley. "All my life," she says, "I worked with a party that meant glory and freedom and brotherhood. You want me to give it up now?" Like Sarah, I don't think he would have been able to.
Ivor Gaber's documentary "Comrades" will be broadcast on Radio 4 on 25 October at 11am