Agents provocateurs tried to persuade Derry civil rights activists 30 years ago to poison the water supply of Ballykelly army base with strychnine, the tribunal was told yesterday.
The claim was made by Mr Hugh Logue, a European Commission official who is currently seconded as a special adviser in the office of the North's First and Deputy First Ministers.
Mr Logue, from Claudy, Co Derry, said he joined the North Derry Civil Rights Association while a student at Queen's University Belfast and became vice-chairman in 1970.
At the time of Bloody Sunday it was believed that the North Derry CRA had been infiltrated by two people linked to the Special Branch, he said, and these two stood out by their attempts to incite the association to commit criminal acts.
"While we remained suspicious of them, we permitted them to remain in [the association]. We were not influenced by them in any way," he said.
Replying to questions from Mr Edmund Lawson QC, for a number of soldiers, Mr Logue said these two people, "what we would call the agents provocateurs that the security forces had within our organisation", had at one stage produced a map of the army barracks at Ballykelly and its water supply.
They had said they had a ready supply of strychnine "and they would have made that available to us", he continued. "We dismissed it out of hand. We could see it a mile away - it was a set-up by the security forces to implicate the North Derry CRA in a violent act, and we would have no part of it."
Asked by Mr Lawson if he was prepared to name these people, Mr Logue said that one was now dead and he had no idea where the other was. Mr Christopher Clarke QC, counsel to the tribunal, intervened to say that, arising from discussions between the tribunal's solicitors and this witness, they knew who the people were.
Mr Logue, who was also on the executive committee of the Northern Ireland Civil Rights Association (NICRA), stressed that there was no link, formal or informal, between the civil rights movement and the IRA.
He also said that gunmen had never used NICRA demonstrations as a front for violence, and the North Derry CRA did not consult with the IRA over arrangements for marches.
He said he was not asked to take part in the organisation of the march in Derry on 30th January, 1972, "save to ask John Hume to participate". He was at a NICRA executive meeting on January 14th, and it was probable that he indicated there that Mr Hume might not participate in the Derry march.
The witness said he thought he would have asked Mr Hume about the Magilligan march (planned for January 22nd) and the Derry march at the same time. He (Mr Hume) would have agreed to Magilligan because he had considerable confidence in the North Derry CRA, which was organising it - "a confidence that did not fully extend to the Derry Civil Rights Association".
Mr Logue said he already had doubts that Mr Hume would attend the Derry march (in the event, he did not). The witness said he thought Mr Hume was alienated from the Civil Rights Association in Derry at the time. In other replies, however, he said he thought the interpretation that Mr Hume was nervous of Derry CRA leaders in terms of their potential political opposition "is without foundation".
Mr Logue described his participation in the Bloody Sunday march and how he took cover in Rossville Flats when British soldiers entered the Bogside. From a window, he saw a soldier lying on the pavement in Rossville Street with his rifle pointed towards Free Derry Corner.
If there was shooting from the flats this soldier would have been a simple target, but he clearly did not feel under any threat as he was not taking cover.
Mr Logue, who has worked in the EU Commission for 15 years and acted as adviser to various Commission presidents, also described helping to carry the bodies of Mr Barney McGuigan and Mr Kevin McElhinney to an ambulance.
The inquiry will sit again next Tuesday.