By 1936, Oswald Mosley's party had been waging a hate campaign against Jews, communists and the Irish in the East End for more than two years.

Accusing Jews of taking "English" jobs, Mosley's elite bodyguard - the Blackshirts - terrorised Jewish stallholders in Petticoat Lane street market, beat up Jews going home after synagogue and covered walls with graffiti.

Copying the militaristic style of the fascist regimes in Germany, Italy and Spain, they carried out a reign of terror. "Perish Judah" and "Death to the Jews" were scrawled all over the East End.

At that time, I was a member of the Labour Youth League and we heard that Mosley was planning a big rally in the East End on Sunday, October 4. We were told to get down to Gardiner's Corner - a famous department store on the edge of the City of London.

It seemed like an act of solidarity because, on the same day, the Republicans in Spain were also preparing to defend Madrid against General Franco's fascists.

I GOT off the 253 tram just after noon and there were already people marching and carrying banners proclaiming "No Pasaran" - the slogan we took from the Spanish Republicans which meant "They shall not pass".

People were coming in from the side streets, marching towards Aldgate. There were so many that it took me about 25 minutes to get there.

I remember standing on the steps of the White chapel Art Gallery, watching Mosley arrive in a black open-top sports car. He was a playboy aristocrat and as glamorous as ever.

By this time, it was about 3.30pm. You could see Mosley - black-shirted himself - marching in front of about 3,000 Blackshirts and a sea of Union Jacks. It was as though he were the commander-in-chief of the army, with the Blackshirts in columns and a mass of police to protect them.

I had already seen him at a public meeting some months before. He'd been standing on the back of a lorry parked outside the Salmon And Ball pub in Bethnal Green and I remember that, along with his Blackshirt bodyguard, he always seemed to be with a lot of large-bosomed women! I can still hear his plummy Oxford accent and, when he spoke of an "alien menace", I realised that he was talking about me and my family - my dad, who was an unemployed tailor, and my uncle Wolfie, who joined the army aged 14 and went on to win a Military Medal.

Back at Gardiner's Corner, Mosley encountered his first setback, thanks to a lone tram driver. About 50 yards away from me I saw a tram pull up in the middle of the junction - barring the Blackshirts' way. Then the driver got out and walked off. I found out later he was a member of the Communist Party.

I remember that, in contrast to the ugliness to come, the weather was beautiful, like a summer day. By mid-afternoon, the crowds had quickly swelled to more than 250,000, with some reports later suggesting that up to 500,000 people gathered there.

As the tension rose, we began chanting "1, 2, 3,4, 5! We want Mosley dead or alive!" and "They shall not pass".

In a bid to keep the crowd away from the fascists, around 10,000 police officers, virtually every spare policeman in London and the south-east, had been drafted in. When the tram stopped and blocked the way, the police decided to charge the crowd in a bid to disperse us. They were waving their truncheons but we were so packed together, there was nowhere for us to go.

I could see police horses going up in the air because some kids in front of me were throwing marbles under their hooves. That made the police more hostile and they spent the next hour charging into us. Then, suddenly, people were waving to us from the back of the crowd.

THE Communist Party had a system of loudspeaker vans and a command post with a phone and team of messengers from which to co-ordinate the action.

But they also had a secret weapon - a spy named Michael Faulkner, who was a medical student and communist sympathiser. Faulkner had infiltrated the Blackshirts.

When Mosley was halted at Gardiner's Corner, police chief Sir Philip Game told him that the fascists could go another way, south through Royal Mint Street and Cable Street.

As Mosley was passing on instructions, Faulkner rushed to the phone near Aldgate Station and rang Phil Piratin, the communist leader. Piratin told those in the loudspeaker vans to transmit the message: "Get down to Cable Street!"

The sheer weight of numbers meant it was a slow procession but I got there in time to watch the battle. I was young and afraid of what was basically a fight between the police and us, because we couldn't get near the Blackshirts. The street is very narrow and there were three and four-storey houses where Irish dockers lived.

In 1953 Stalin died, and the floodgates of Moscow started to open. There was only a trickle at first, and it was another three years before anything like the full story of the Stalinist terror could be told. We still do not know how many people were murdered, only that the killing went on right up to Stalin's death, that torture was routine, that tens of millions died. Stalin's terror was on such an unimaginable scale that a million or two more or less killed and tortured would barely affect our perception of it. Stalin was defended by sincere Communists for whom the years after 1953 were ones of dawning horror. How they coped, and whether they kept the faith, depended entirely on the individual.

Phil Piratin, out of Parliament and a full-time Party worker, remembers: "Sometimes at our political committee meetings after Stalin's death, Harry Pollitt would take from his pocket a piece of paper, and say that the Czech ambassador had given him the following names of people who had been ... what was that word they used? Terrible word! Horrible word! Rehabilitated, that's it." A terrible word because to be rehabilitated you must already have been condemned and shot, probably after being tortured. "It used to hurt me. Since then I sometimes try to ascertain how others felt. It's something we all still find hard to talk about."

At one of these meetings a Czech surname was read out which caused a sudden sick feeling in Piratin's stomach. "I asked Harry to give us the full name. Harry just looked at me. My wife and I were friends with this man and his wife, they used to come to our house in Hampstead, we went to their flat in Kensington. Then in 1949, they were due to come over one night, and his wife phoned up and said he'd been called away. A few weeks later my wife phoned the flat. There was a new voice, it said our friends had gone back to Prague. We never heard from them again. Now I knew why. "I thought: do I tell my wife? I told her in the end. She was very distressed. It was the start of a long period of distress. She felt sick at heart, as I did. Those things live in you, the look in my wife's face when I told her."

Piratin never left the CP. But his heart had gone out of the work, and he quietly resigned all his Party posts. With a little money of his wife's, they went into business together, and, as he puts it, "prospered". But the previous generation of Communist leaders was far closer to it all than Piratin. Harry Pollitt, Johnny Campbell and Bill Rust were all frighteningly close to the terror. Wives, children, lovers - for them the terror laid its cold hand on their lives in the late 1930s and never let go. The leaders of the Comintern generation were now so locked into what happened in Moscow that they must either break with their life's work or rationalize what was happening.

For five years, from 1945 to 1950, there were two Communist MPs at Westminster - William Gallacher and Phil Piratin. Though they were very different in origin, age and temperament, most Communists felt they made a very good parliamentary double-act.

Gallacher, elected in 1935, was the Clydeside agitator who punched the Chief Constable at the Battle of George Square in Glasgow at the time of the 1919 strike for the 40-hour week. Piratin was the East Ender whose organising abilities brought 100,000 Londoners on to the streets in the Battle of Cable Street in 1936 and stopped Mosley's Fascists from marching through Whitechapel.

The two class warriors never aspired to be great Parliamentarians in the conventional sense, but after Piratin was elected in Mile End in 1945 they worked the system effectively as a parliamentary group of two, officially recognised by the Speaker. Years later, in a long interview with Kevin Morgan, biographer of Harry Pollitt, Piratin described how he used to answer questions at meetings about his relations with Gallacher: "It's quite simple: there are two of us and Gallacher is the elder [64 compared with 38], and therefore I automatically moved and he seconded that he should be the leader. He then appointed me as Chief Whip. Comrade Gallacher decides the policy and I make sure he carries it out."

In fact, of course, the policy was that of the Communist Party, to whose executive committee and political committee Piratin was elected after he became an MP. I recall him making forceful contributions to the discussions in both bodies, and because of his position in Parliament and his work in the East End and on Stepney Borough Council, to which he had been elected in 1937 (the first Communist councillor in London), he was always listened to with attention and respect.

In Parliament one of his proudest achievements was the tabling of a Private Member's Bill, on safety in employment, with the support of a number of Labour MPs. In the event it was withdrawn when the Minister of Labour agreed to incorporate some of its points in the Labour government's future programme. A less happy experience was his censure by the Commons Committee of Privileges for a fight with a journalist whom he said had abused him as a Jew and a Communist, though the journalist was also censured.

Even if he had not become an MP Piratin's record would have ensured him a place in the party leadership. Born into an orthodox Jewish family, he began to have doubts about his father's religious beliefs as a schoolboy during the First World War. He was shaken when he saw that the Chief Rabbi of Germany was calling on Jews to fight in the Kaiser's army and the Chief Rabbi of the UK was calling on Jews to fight in the British army. It was abhorrent to think of one Jew fighting another.

The General Strike of 1926 and the hunger marches of the unemployed, combined with wide reading of books on social and political questions borrowed from the Whitechapel Library, further stimulated his interest in politics. He finally joined the Communist Party after the Mosley rally at Olympia on 7 June 1934, when hundreds of anti-Fascists were beaten up by the Blackshirts. "That night," he wrote in his 1951 memoir Our Flag Stays Red, "I was proud of the anti-Fascists, the working class, and particularly the Communist Party. I could have kicked myself for not being a member of a party whose lead I was so proud to follow." Then began a period of ceaseless activity as leader of Stepney's Communists. A major part of his work was helping tenants to organise for repairs and against evictions. The Stepney Tenants' Defence League won significant concessions for tenants, sometimes through threatening legal action, but more often by hitting the landlords where it hurt by rent strikes in which thousands took part.

In the Second World War Piratin volunteered for the Royal Navy, but was refused entry, despite an appeal to the Home Secretary, Herbert Morrison. He became an air-raid warden, and was appalled by the conditions in the shelters for working people compared with those for the rich. To draw attention to the scandal he organised an invasion of the luxury shelter at the Savoy Hotel by 70 men, women and children. They demanded refreshments in the form of tea and bread and butter, but were told that the minimum charge for anything at the Savoy was 2s 6d. Eventually the waiters and management were persuaded to serve tea and bread and butter (on silver trays) at the Lyon's teashop price of 2d. The propaganda coup received wide publicity, followed shortly after by the party's challenge to the Government's refusal to open the tubes as shelters. The gates broken down when the air-raid sirens sounded, the Government gave way, the tubes were opened, refreshments and first-aid facilities provided and bunks installed.

Later in the war Piratin became the Communist Party organiser in West Middlesex, playing a big part in increasing production in the arms and aircraft factories there, and greeted by the sentry on the door with "Good morning, Phil" when he went into meetings of the Communist Party group.

In 1950, as the Cold War intensified, both Piratin and Gallacher lost their seats. Piratin then became circulation manager of the Daily Worker, leaving in 1956 to go into business.

He remained in demand as a popular speaker at Communist gatherings, and historians, journalists and television and radio producers frequently interviewed him. After the Communist Party transformed itself into the Democratic Left he became a supporter of the new organisation.