[2][3] Walsh joined the IRA in the wake of the August 1969 riots in Belfast in which Bombay Street a Catholic/Nationalist area was burned to the ground by a Loyalist sectarian mob, 1,820 families (mostly Catholics) had to be evacuated and the British Army sent in to keep the peace.

On 8 March 1973 at about 06:00 am, Roy Walsh and Gerry Kelly primed their car bomb which weighed about 100 lb and drove to the Old Bailey, three other bombs were planted by other IRA volunteers around London and all timed to go off at roughly the same time.

Before the bomb went off Walsh along with nine other members of his team were caught trying to leave the country at Heathrow Airport and detained there and then.

[2][8] At his trial on 14 November 1973, Roy Walsh received life imprisonment for the bombings and 20 years for conspiracy along with seven other IRA volunteers.

[1] In an interview with Peter Taylor, Walsh said that he was "shocked that there was so many casualties because our intention was never, never to injure anyone" and that given the warnings, "it was the slowness of the police reactions that caused the injuries."