A group of men who had become known as the Birmingham Six walked free on this day in 1991 after spending 16 years in jail for a crime they did not commit.

The six men - Paddy Hill, Hugh Callaghan, Richard McIlkenny, Gerry Hunter and Billy Power, all from Belfast, and John Walker from Derry - were convicted for the murder of 21 people after bombs exploded in two Birmingham pubs in November 1974.

Five of the men had left Birmingham on the day of the attack to attend the funeral of a former IRA man in Coventry. They were arrested en route and taken to Morecambe for forensic testing, before being taken into custody by the West Midlands Serious Crime Squad.

Callaghan, McIlkenny, Power and Walker signed confessions, which they later said they were forced into after interrogation and beatings at the hands of police officers; the statements were accepted as evidence when their trial began in June 1975.

[Read more: April 24, 1993 - IRA’s Bishopsgate bomb devastates the heart of the City of London]

Forensic tests claimed to show that Hill and Power had handled explosives on the day of the attack. The jury found all six men guilty, and on August 15 they were sentenced to serve 21 life sentences each.

The men would lodge their first appeal the following year, but it was dismissed. It was only after journalist Chris Mullins – later a Labour MP and minister – released a book about the case after researching it for TV show World in Action, that pressure began to grow for a new investigation.

Another appeal in late 1987 failed, but over the following three years various newspaper articles, documentaries and books brought forward new evidence to further question the safety of the six men’s convictions.

A final appeal occurred in 1991 after details of fabrication and suppression of evidence came to light, the Court of Appeal categorised the forensic evidence which had helped to convict the Six as “wrong, and demonstrably wrong, judged even by the state of forensic science in 1974”.

The men were immediately released, with Paddy Hill claiming they had been used as “political scapegoats”. A decade later, the six men were awarded compensation ranging from £840,000 to £1.2 million.

Also on this day: March 14, 1938 - Hitler receives a hero's welcome on his return to Vienna