A witness yesterday described how he came on soldiers concealed in a building inside the Bogside perimeter shortly before the main force of paratroopers rushed in and the killings took place.
The incident outlined by Mr Frank Bradley is the first evidence that soldiers were positioned so far forward, south of William Street and overlooking Rossville Street, as the civil rights marchers arrived.
Mr Bradley said he was in a massive jam of people as the march stopped at William Street and the word passed back that there was a confrontation with the British army at a barricade.
He heard rubber bullets fired and then was affected by tear gas, and the crowd started running in all directions. He went down an alleyway south of William Street, leading to a yard known as B.G. Fox's yard.
When he climbed a 9ft wall he saw six or more soldiers in the yard on the other side, facing towards Rossville Street and the Bogside flats. "They had gas masks and they had all the paraphernalia for a war . . ."
Mr Bradley said the soldiers did not see him and he paused there only for seconds. "I cannot say whether or not the soldiers were firing their rifles. It was a very scary situation," he said.
He ran back to William Street and tried to get out of the area. But he felt trapped when he saw soldiers in Little James Street in front of him and army vehicles advancing, so he ran down Rossville Street.
Mr Christopher Clarke QC, counsel for the tribunal, suggested he might be mistaken in thinking he saw soldiers south of William Street then, and that what he saw was soldiers north of there.
Mr Bradley insisted, however, that he had seen the troops inside the Bogside, "in ahead of the parade . . . They were already in there."
Mr Edmund Lawson QC, representing soldiers, commented: "I adopt the suggestion made by Mr Clarke in relation to this witness being mistaken about troops being to the south of William Street at that time."
Later Mr Bradley confirmed to reporters, when shown aerial photographs, the premises where he came on the concealed soldiers. He was adamant about the incident.