A former paratrooper whose rifle fired the shot which killed a teenager on Bloody Sunday, is expected to give evidence at the Saville Inquiry today.
"Soldier F", who was a lance corporal in the anti tank platoon, is the only soldier whose rifle has been forensically-linked to the death of one of the 13 civilians shot dead during a civil rights march in Derry's Bogside in January 1972.
Tests showed that 17-year-old Michael Kelly was killed with a shot from Soldier F's rifle. During the Widgery Tribunal held soon after Bloody Sunday, Soldier F said he fired at a man about to throw a nail bomb. But Lord Widgery was not satisfied that Mr Kelly was throwing a bomb when he was shot.
It has been established that Soldier F fired 13 shots on Bloody Sunday. He was also one of four soldiers who were in Glenfada Park North, where four civilians were shot dead and five wounded.
Last October, another witness, "Soldier 27", alleged that Soldier F had kneeled in front of him and opened fire on the crowd at the Rubble Barricade in Rossville Street.
"Two people towards the centre of the barricade fell within seconds of each other in the opening burst of fire," Soldier 27 said. "I didn't see anyone with a weapon or see or hear an explosive device."
Soldier 27 said he had a vague recollection that the officer in command of the Parachute Regiment on the day, Derek Wilford had said that soldiers F and G, who has since died, would be better packed off to the SAS.
Around 200 relatives of the victims have travelled to London to hear Soldier F give evidence at the Central Hall in Westminster.
The inquiry is currently hearing evidence in the capital to help protect military witnesses but will return to the Guildhall in Derry in just over a month's time.