Several of these cases, like Mr McNamee's, have followed terrorist bombings.

Gerard Conlon with his sister

• The Guildford Four, Paul Hill, Patrick Armstrong, Carole Richardson and Gerard Conlon, was the most famous case.

  Five people were killed by explosions in two pubs in Guildford, Surrey, in October 1974. They were released in October 1989 after the Court of Appeal found their convictions had been unsafe.

  In 1993 the detectives at the centre of the case were cleared of fabricating evidence.

• The Birmingham Six, Paddy Joe Hill, Hugh Callaghan, Richard McIlkenny, Gerry Hunter, Billy Power and Johnny Walker, spent more than 16 years in prison for the murder of 22 people in 1974. The explosions at two pubs in Birmingham left 162 people injured.

  They were freed at the Old Bailey in 1991 when the Court of Appeal quashed their convictions after finding that evidence had been fabricated.

  Prosecutions against police accused of tampering with the evidence were halted in 1993.

• The Maguire Seven were jailed in 1995 for running a bomb-making factory, but their conviction was quashed in 1991.

Anne Maguire: Conviction quashed

John Kinsella was jailed for 20 years for taking part in the Warrington gasworks bombing in 1993, which was later reduced to 16 years. Despite the IRA not claiming him as a member, and Kinsella denying being involved in terrorism, he lost an appeal against his conviction earlier this year.

However, not all controversial cases have been related to Northern Ireland.

• Last year, three people convicted of killing newspaper boy Carl Bridgewater in 1978, James Robinson, Michael Hickey and Vincent Hickey, were released. They had spent 17 years in prison.

• And Derek Bentley, who was hanged after being convicted of killing PC Sidney Miles in 1952, was pardoned 45 years later.

  In pardoning Bentley, the Lord Chief Justice was highly critical of Lord Goddard who had sentenced Bentley to death. Bentley had been denied a fair trial, Lord Bingham said, which was the "birthright of every British citizen".