One of the enduring images of Guildford Four is of Gerry Conlon bursting out of the Old Bailey in London to a sea of television cameras, his fist raised in triumph after 15 years in prison.

Gerry, along with Paul Hill, Carole Richardson and Paddy Armstrong, had been jailed for life in 1975 for an IRA bombing which killed five people and injured dozens more. It was 1989 before the wrongful conviction was overturned and they were allowed to walk free.

As Conlon made an impassioned speech outside the Old Bailey calling for the release of the Birmingham Six, Paddy Armstrong left quietly by the back door. After a decade and a half of confinement, his first moments of freedom were a much quieter affair.

In the last 28 years, Paddy Armstrong has remained a low key guy. Now married with two children, he has written a memoir, aptly titled 'Life After Life'. Paddy was Marian Finucane's guest on Saturday, along with his solicitor, Alistair Logan, who worked tirelessly for Paddy's freedom until his release.

As Alistair told Marian, he knew early on that Paddy was innocent. 'I had formed the view that Paddy wasn't guilty of the offences, and that the confession that they extracted from him had been done under duress and violence,' he said. The lawyers for the other accused also believed that their clients were innocent.

Paddy and Paul Hill each received 35 years in prison in 1975, the longest sentences handed out by the British justice system. The same year, four IRA men were arrested after a standoff with police which became known as the Balcombe Street Siege. As Alistair told Marian, they were asked about the first offence they committed when they came to England. They said, 'Guildford'.

'"And the police officer who was interviewing them said, 'You mean the Guildford bombing?' And they said yes. [The police said] 'Do you mean we got the wrong people for that?' They said yes. 'Oh', they said, 'This is very serious, we must investigate it'. But in fact, they never came back and asked them another question about it.'

Despite spending 15 years behind bars because of an act carried out by the IRA, Paddy never felt anger towards the group. The blame lay with the police, he said, because they were unwilling to admit their catastrophic error.

'When the Balcombe Street people were arrested, they admitted to it. And they were all willing to go to court. [The IRA] came up to me and said there was nothing else we could do. In the end it was still down to the police. They knew that we didn't do anything.'

As MP Chris Mullin said of the case, 'small lives were thrown away to protect great reputations.' Paddy credits his wife, who he met in Dublin, for helping him to redeem his life and live as he could only have dreamed of in prison. Does he feel angry? 'Not anymore,' he said, 'Being that way would have ruined my life and my family's life…..I am living life to the full.'

Life After Life: A Guildford Four Memoir is published by Gill Books.

To listen to the full interview, click here.