Martin McGuinness has agreed to give evidence at the inquest of Seamus Bradley, who was shot dead in Londonderry on the day of Operation Motorman - July 31, 1972. Mr McGuinness has acknowledged that he was a senior member of the IRA in the city at the time.
The question lawyers want to put to him concerns whether or not a deal was made between the Army and the IRA to allow the barricades in Belfast and Derry to be taken down without resistance.
If the deal had been made, then the soldier who shot Seamus Bradley had little reason to fear that he was about to come under attack.
Gerry Adams has also been asked to give evidence, but says he has nothing to offer. He was, indeed, party to negotiations with the British in previous weeks.
But those negotiations had been around the agreement of a ceasefire earlier in the month and that ceasefire had ended three weeks before Operation Motorman.
However, that does not mean that all back-channel communications between the British and the IRA had stopped. In later years such communications would be conducted at times of extreme violence and high tension.
And, looking back at Operation Motorman, it seems to have the characteristics of a well-orchestrated avoidance of conflict. The Army had already learned that it could deal with the IRA.
In the run-up to the breakdown of the July ceasefire senior members of the IRA - including Seamus Twomey, accompanied by the Price sisters - had been able to walk into Army bases in west Belfast and sit down to negotiate with senior officers.
The IRA had proven itself capable of commanding a total halt to operations, though it had also shown itself to be mischievous in testing what latitude it could take for itself.
Belfast and Derry were in chaos. The barricades in nationalist and loyalist areas had been reinforced from the original piles of furniture and burnt-out cars to concrete bollards and metal pillars.
These created a huge challenge to the Army. The GOC Harry Tuzo had, during the two-week ceasefire, prepared for the Government his own analysis of what would be required to defeat the IRA in the event of the anticipated ending of the ceasefire.
Tuzo estimated that the Provisional and the Official IRA between them had 2,000 men. The Army should now, he thought, be ready for a major "firefight" to demoralise and neutralise them.
He did not think that British public opinion would accept a long campaign against the IRA and therefore recommended that the job of wiping them out should be completed in a matter of weeks.
He wrote to Secretary of State William Whitelaw: "It is unrealistic to think in terms of total elimination; complete demoralisation and surrender is the best we can hope for."
He wanted the Army to be free to use heavy weapons like the Carl Gustav, a type of anti-tank bazooka, in offensive operations against the IRA in Belfast housing estates.
His plan included an attempt to persuade Catholics that this was all in their best interests.
"Indeed, our information policy would aim to attract support from Catholics in the north as well as in the Republic for ridding society of a force that would otherwise bring about civil war with dire consequences for Catholics in Ulster and every likelihood of spreading south of the border.
"The fact that low-key military operations and sincere political proposals have been tried and failed must be emphasised."
But the British response, when it came, did not proceed as Tuzo had foreseen.
The IRA did indeed end its ceasefire, as he predicted, and it escalated its campaign, notably with large-scale bomb attacks like Bloody Friday, 10 days before Operation Motorman.
The Army made a dummy run on its invasion of the no-go areas by saturating the Lenadoon estate in west Belfast.
Republicans staged a massive propaganda response by leading a large part of the population out of the estate on a Sunday afternoon, saying they couldn't live with the Army squatting among them. Several of those families went back after the protest. Many took shelter for several nights in a school on Slievegallion Drive.
I went there as a young reporter and met with two members of the Provisionals' Belfast Brigade - Gerry O'Hare and Jimmy Drumm - and they invited me to accompany them on a drive around the area. We ended the night at the home of Tom Conaty, a member of an advisory committee set up by Whitelaw.
I don't know what Conaty thought I was doing in his house. He must have thought I was an IRA man too. O'Hare and Drumm briefed him on what they had seen that night, details about conditions at the school and so on.
Conaty was certainly a back channel to Whitelaw at that time. Another back channel had been established in Derry by RUC inspector Frank Lagan, a decent man much reviled by the Army, which didn't like his close acquaintance with the Catholic community.
So, the question raised by Bradley family lawyers about whether an agreement had been made between the Army and the IRA to minimise casualties during Operation Motorman can be answered.
And the likely answer is that there was such an agreement - given that Tuzo's plan to crush the IRA using bazookas against snipers was so much watered down and the IRA, for its part, withdrew to avoid a massive battle it couldn't hope to win.
The message to Catholics warning them of the danger and pleading for their support was reduced to a simple televised announcement by Whitelaw that the Army would move in and take down the barricades.
Tuzo was denied his big battle and Whitelaw's gentler management style prevailed.
In retrospect, it looks more like a diplomatic than a military victory. Not that the IRA was wholly inactive.
It bombed Claudy that day, killing eight people, and has never admitted responsibility. Maybe that bombing was in breach of a deal with Whitelaw.
Another IRA man I have spoken to claims that he and Tucker Kane - now dead - opened fire on soldiers in the Stewartstown Road area and wounded one of them.
But there was no resistance to the invasion of the no-go areas themselves. The Army practically encircled west Belfast with new camps and occupied three Catholic schools and the GAA's sports ground at Casement Park.
This gave it a reach inside these communities that enabled it not only to patrol the streets more thoroughly, but to recruit spies. From then on the annual casualty figures declined.
I suspect there is a story to be told about how Tuzo's anticipated battle was avoided. The inquest of Seamus Bradley is as good a place as any to start telling it.
Malachi O'Doherty's unauthorised biography of Gerry Adams will be published by Faber & Faber in May