Denis Donaldson murder: The unanswered questions that bedevil Gerry Adams
Killing the self-confessed MI5 spy sent a message to other republican informers: whatever you say, say nothing
Several questions arise from the BBC NI Spotlight programme on the murder of Denis Donaldson. Why did the IRA kill him? The easy answer is that it was executing an informer, as it had done many times before. But the war was over. The arms had been decommissioned. Donaldson was no further obvious risk to them if they were going to dismantle the IRA machine.
Killing him to deter others from informing made little sense, if there was to be less criminal activity to inform on.
Of course, the IRA would go on importing weapons from America, so secrets had to be protected, but there was another possible motive.
The movement, we now know, was riddled with informers. The RUC in the mid-1990s believed that the Provisionals had about 600 members. Dennis Bradley's estimate, having seen the files, is that the state had even more informers - at least 800.
Had Donaldson not been killed, other informers might have seen the chance to come out and declare that they had been working for the state, clear their consciences, explain themselves and trust that they would not be shot.
Was the killing of Donaldson designed to prevent a flood of informer disclosures which would have shamed the IRA? Here's another question.
Just a little over a year before the murder of Denis Donaldson, the PSNI received intelligence that the Provisional IRA had robbed the Northern Bank and made off with £24m. The Chief Constable, Sir Hugh Orde, disclosed that information to the media.
After the murder of Donaldson, the Special Branch had an agent - at least one - who knew that the Provisionals had killed him, yet the police chose not to disclose that and let the blame rest with the dissidents.
They had one strong reason to be coy.
The IRA had completed its decommissioning, or as much as it intended to complete, and only one further obstacle remained to Sinn Fein being accepted as a partner in the executive by Ian Paisley's DUP. That obstacle was the refusal of Sinn Fein to endorse the police.
After the Northern Bank robbery and the shocking murder of Robert McCartney in January 2005, the Provisionals were discredited as never before and brought under enormous pressure to concede to keeping within the law.
Had we known that they had murdered Donaldson a year after the murder of Robert McCartney, their credibility would have been eliminated and the political process would have died.
One has to suppose that this prospect featured in the decision of the police to let us all imagine the Provisionals had nothing to do with the murder. Paisley was waiting for a Monitoring Commission report in October of that year to clear the IRA.
Jonathan Powell, Blair's envoy to Adams and McGuinness, later wrote: "It didn't look like an authorised operation and the furore died quickly, with everyone apparently determined not to allow the murder to knock the peace process off-track."
If Adams, as is claimed, really did sanction that murder, he was taking an enormous risk. He was in danger of being left stranded, months after decommissioning, with no political gains to show for his decades-long project.
One of the illuminating claims of the Spotlight programme came at the end, from former head of RUC Special Branch Raymond White.
White said that the IRA had realised in the "late-Seventies, or early-Eighties" that the armed campaign would fail and that it had to put its energies into political activism.
He says the republicans had put their best efforts into their war and worked out that this wasn't enough.
Consider the implications of that claim. They are that the whole IRA campaign after that was not a war for the ejection of Britain from Ireland, but something else.
In the early-Seventies, the IRA really believed that it could make Northern Ireland too hot for the British to handle and they would drop it. They were wrong.
As a British official put it to Gerry Adams on the flight back from talks with William Whitelaw in July 1972, the Army lost more soldiers in road accidents than were being killed in Northern Ireland.
In the late-Seventies, the period which White referred to, the IRA had men and armaments, but it did not have a strategy.
This was when Gerry Adams, its chief new theorist, came out of Long Kesh, having been interned in 1973 and then convicted of attempting to escape.
He did a few things straight away. He ended the feuding with the Official IRA. He put to rest the myth that the Brits were leaving, something they had encouraged the naive republicans to believe. And he urged the bolstering of Sinn Fein, under the direction of the IRA, of course.
From then on, the two wings of the movement would take separate courses. Adams believed, one presumes, that they would have a symbiotic relationship; that each would help the growth of the other.
But one thing is clear: whereas, in 1970, the IRA was recruiting huge numbers, by the late-1970s, it preferred to stay small.
In Long Kesh, the IRA had trained for the combat conditions of the civil war that would inevitably follow the British withdrawal they naively anticipated and the contradiction was clear; that once the IRA had lit the fuse, it would be for others to contain the blast and clean up afterwards.
The IRA had no future without a political party so big that it could not be excluded in the way that the IRA inevitably would be.
The IRA's fate was to be a bargaining chip in future negotiations and it would only be possible to deploy it in that way if it was kept small and under control.
In 1986, Gerry Adams appeared on Brian Garret's programme on Radio Ulster with John Hume, the first effort to establish dialogue between the parties.
Adams offered talks to Hume and Hume spurned them, saying that he wanted to talk to the people in charge of the IRA. This is perhaps the only instance of Adams being accused in public of not being the leader of the IRA.
Adams repeated the nature of his problem twice on the programme.
"There are, and one wouldn't profess otherwise, there are certain contradictions between armed struggle and electoral support and we have seen some of that in the past."
So, Adams had acknowledged that the IRA was working against the interest of his political project, though, at the same time, he said that it was for the IRA alone to decide on its strategy.
The man was living at the heart of a massive paradox, or he was backing two horses against each other.
But he surely saw that the tension between the political and military projects would grow and that a choice would have to be made between them.
Throughout the 1980s and into the 1990s, the IRA campaign was a steady drumbeat of bombs and shootings - mostly kneecappings. This is absurdly called a "war".
And when Sinn Fein's growth peaked among those who would tolerate that drumbeat, it stopped. The function of the guns and explosives after that was to provide a bargaining counter. The refusal to decommission delivered more political gains than the weapons in use had.
Read backwards, this seems to have been the fulfilment of a cunning plan hatched in Long Kesh in the late-1970s to make the IRA a political tool of Sinn Fein and take power through politics.
However, life is never that simple and predictable.
But Gerry Adams is either one of the cleverest of strategists, or the luckiest.
Today, hundreds of former agents in Belfast and Derry and Tyrone and South Armagh could illuminate the whole murky story for us, but they remain silent, knowing that talk now is still too dangerous.
The shooting of Denis Donaldson was a message to them: keep your head down and say nothing.