Paddy Hill, who has died aged 80, was the angriest and most articulate of the Birmingham Six – the innocent men convicted in 1975 of the Birmingham pub bombings. The explosions in two city centre pubs in 1974 killed 21 people and injured many more, and took place at a time of frequent IRA terrorist attacks on mainland Britain.

From the outset Hill protested his innocence, to anyone he thought might be able to help. First responses were not encouraging. Tom Sargent, the secretary of Justice, the British section of the International Commission of Jurists, wrote: “In a case like yours so many reputations are at stake that in my view the obstacles to overcome are insuperable.”

It was Hill who first encouraged me to begin the investigation that eventually led to the quashing of the convictions 16 years later. He also managed to convince the Tory MP Sir John Farr that he was innocent. Farr became a valuable ally during the long campaign to reopen the case.

A first application for leave to appeal was turned down in 1976. I helped to make three World in Action documentaries on the case and wrote the book Error of Judgement (first published in 1986, and updated last year), which led to the case being reopened. After a six-week hearing in 1988, the court of appeal upheld the convictions, but new evidence continued to come to light, and the men were at last freed in March 1991, when the appeal court judges found the convictions to be “both unsafe and unsatisfactory”.

Hill spent most of his sentence at HMP Gartree in Leicestershire. He was for many years the one whose spirit seemed to have been least dented, but by the end the strain had begun to tell. His weight fell dramatically and his behaviour was sometimes impetuous. He became involved in various incidents that led to him being sent to cool off with short spells in other prisons. He later estimated that he spent as much as half of his time in prison in solitary confinement.

Hill was born and brought up in Ardoyne, a Catholic enclave of north Belfast surrounded by loyalist strongholds. Even so, he did not come from a particularly republican family. His father and several brothers served for many years in the British army. At the Holy Cross primary school in Ardoyne, Hill became acquainted with James McDade, a boy two years his junior with whom he used to walk home from school. The relationship was to prove fateful.

Many years later, in 1974, McDade would blow himself up while planting a bomb outside the telephone exchange in Coventry. Hill and four friends were on the way to McDade’s funeral in Belfast a week later when they were arrested and charged with the pub bombings. A sixth man was arrested later.

In 1960, Hill’s father migrated to Birmingham in search of work and most of the family soon followed. Hill’s years in Birmingham were turbulent. He collected 17 convictions, mainly for brawling, but also for breaking and entering. In 1970 he served 13 months in prison for stabbing three nightclub bouncers in a fight. Short, stocky and with a deep scar running from his mouth to his chin, Hill might have been considered to have a menacing appearance, but for a ready smile and a devilish sense of humour.

He was not obvious IRA material. Aside from his generally chaotic lifestyle, he had difficulty even raising the fare to Belfast for McDade’s funeral on the day of the bombings, 21 November 1974. At the last minute, he scrounged the money off a nun at a local convent where he occasionally did some painting and decorating.

Although, while in prison, Hill proved to be the most resilient of the six, he had great difficulty adjusting to life outside. Unable to resist the lure of a microphone, he was on several occasions in trouble for making inflammatory remarks.

He emerged from prison deeply damaged. His long-suffering wife, Pat, whom he married in 1966, had divorced him in 1983 when he was still in prison, and relationships with his six children swiftly broke down. He worked for a while as a cook at a community centre for elderly people in Camden, north London, and entertained them with stories of prison life.

Unlike those convicted with him, Hill was never able to shake off having been one of the Birmingham Six. In 1995, with the help of a journalist, Gerry Hunt, he published an autobiography, Forever Lost, Forever Gone.

In 2001 he used some of his compensation (and the libel damages received from several newspapers that carried on asserting that the Birmingham Six were guilty, even after the convictions had been quashed) to set up an organisation, Mojo, which campaigns for victims of miscarriages of justice and provides psychological and other help to the innocent upon their release. Mojo also provides placements for students of law and forensic science.

For years after his release Hill remained deeply traumatised by his experience. “Every morning when I wake I am like a lunatic,” he said at one point. “I’m so tense and wired up I could pull the place apart at the seams. I wish I was back in my cell.” In 2008, he told an interviewer: “I’ve been out for 17 years and I’m still angry.”

He remarried in 2005 and settled on a farm in Ayrshire with his wife, Tara Babel, an artist, who survives him.

• Patrick Joseph Hill, born 20 December 1944; died 23 December 2024