DES WARREN was half of the Shrewsbury Two, the pair of “flying pickets” who were imprisoned under Edward Heath’s Conservative Government after the building workers’ strike in the summer of 1972. Along with his co-worker Ricky Tomlinson, now a noted actor, he was tried and imprisoned for conspiracy after allegations of intimidation and violence which prompted the Government to order a substantial police investigation. Warren, and scores of supporters, maintained for decades that he had been a scapegoat of the system and a prisoner of conscience.

Desmond Warren was born in Boughton, Chester, in 1937. He left school at 15 to train as a chef, then did National Service in the Royal Horse Guards before becoming a steel fixer, laying steel rods in reinforced concrete. He worked on the Barbican site in London at the end of the Sixties, but when he decided to become a shop steward for one of the unions, he was laid off. Moving home to the Chester area, he worked where he could, but as a union member he found that his name was nationally blacklisted among employers.

At the beginning of the Seventies, the poor safety record and low wages of the construction industry were already causing unease among workers and unions, and the “lump” — the system of labour-only cash payment that encouraged casual labourers, rather than those willing to ply a trade — was another source of discontent. Proposing a “builders’ charter”, which included demands for a minimum wage, a pension scheme and a 35-hour week, the Transport and General Workers’ Union and the Union of Construction, Allied Trades and Technicians called a strike for June 1972.

Thousands of workers on major sites across Britain came out in support, but many on smaller operations did not. Local committees therefore began to send out busloads of pickets to sites which were reneging on the strike, or which had never joined it, to persuade them of the necessity of the protest, and it was during these actions — for which there is no unbiased account — that the events allegedly occurred which prompted Des Warren’s trial.

The builders’ strike lasted all summer, and when it ended in September the unions’ demands for pay increases were met. But the National Federation of Building Trades Employers almost instantly presented to the Government a dossier submitting that the pickets had threatened and beaten workers on their sites during the strike, and the Home Secretary, Sir Robert Carr, decided to take action. Policemen carrying sets of photographs, with certain faces marked, began to canvass the Shrewsbury area; and Warren and Tomlinson were eventually arrested, with four others, in a series of raids.

Their trial ran from October to December 1973, to a background of angry protests and marches outside. One of the main points at issue was the decision to charge Warren and Tomlinson with conspiracy, a crime which carried no maximum sentence. If they had been indicted for the crime at the centre of the conspiracy charge — the intimidation of workers to abstain from work — the maximum sentence would have been three months.

As it was, Warren got three years, Tomlinson two. “You are no martyr,” pronounced the judge. “You have the power of speech and the power of leadership, which you apparently used to ill purpose. You thought you could flout the law. You were wrong.” Warren riposted that “the conspiracy was between the Government, the employers and the police”, but to no avail. An appeal against the two men’s sentences failed.

While in jail, they protested by wearing nothing but blankets and refusing to do prison work. Both also tried hunger strikes. Outside, workers marched from Liverpool to London to solicit their release, and questions were raised in Parliament. Yet the Trades Union Congress was unwilling to make strong representations for their release, since Harold Wilson’s Labour Government had come to power in 1974 and they did not want to rock the boat. This rankled with Warren. “The TUC leaders had the key to my cell in their pocket all the time,” he said, “but they never used it.” In Parliament, Labour MPs attempted to brand him a political prisoner, and were met with Tory cries of “He is a political thug”. Amnesty International avoided taking him on as a cause, deciding that he did not “fall within our statutory definition of a prisoner of conscience”. And Warren developed, in prison, the symptoms of Parkinson’s disease, which he argued were attributable to the tranquillising drugs administered by the prison authorities.

He served all but four months of his sentence. Upon his release, he was defiant. “My sentence was to have been a deterrent to trade unionists,” he said. “It appears that trade unionists are not deterred . . . and neither am I.” He threatened legal action against the Home Office for his treatment in prison, and was compensated with a £3,000 settlement, but he found it difficult to find or to sustain work. In 1982 he published The Key to My Cell, which detailed his experiences of the justice system. Last year he and Tomlinson were presented with the Robert Tressell Award by the National Construction Safety Campaign, for services to working people.

He is survived by a large family.

Des Warren, trade unionist, was born on October 10, 1937. He died of pneumonia on April 24, 2004, aged 66.