Did a British military intelligence agent within the republican movement control a garda informant for the IRA, and were a garda's tip-offs used by terrorists to set up two senior RUC officers for assassination?
Could British intelligence have warned those police officers of the danger they were exposed to, and did they decide not to intervene, to protect their agent? Is the Irish government sidelining such questions by limiting the scope of the Smithwick tribunal into those two deaths?
It may sound like the plot of one of Colin Bateman's black northern comedies, but these questions are being asked by a conservative, even pro-establishment, lawyer from Co Down. John McBurney is best known as the family solicitor of the DUP luminaries Ian Paisley and Peter Robinson and, although not a member, often acts for the party too. He has a reputation for sober judgment. DUP insiders say he has often been a restraining influence, discouraging rash legal actions and counselling caution.
McBurney is representing the family of chief superintendent Harry Breen, a native of Banbridge. On March 20, 1989, the commander of the RUC's H Division was travelling home from Dundalk garda station with a colleague, superintendent Robert Buchanan. They were on the Edenappa Road, just north of the border, when they were shot dead at an IRA road block near Jonesborough.
Up to five terrorists were directly involved. Buchanan, the driver, tried to reverse away. When his body was found, the car was in reverse gear and his foot was on the accelerator. Breen was lying by the roadside. The Vauxhall Cavalier they were travelling in, the Buchanan family car, was riddled with 25 bullet holes.
The IRA put its success down to a chance encounter, and claimed its volunteers thought their lives were in danger. It certainly didn't look that way and, in any case, RUC officers were not allowed carry arms in the republic.
"The operation to attack and kill these men was not planned on the day as a one-off," said McBurney. "I am convinced, from all I have gleaned, that it was a matter of weeks, perhaps months, in planning."
The ambush followed a particularly sensitive meeting at the Dundalk office of garda chief superintendent John Nolan. It had been called at short notice to discuss a co-ordinated push against smuggling, in particular against the alleged activities of Thomas "Slab" Murphy, the IRA chief of staff who lived in Ballybinaby on the nearby Louth/Armagh border.
The IRA later claimed it had recovered intelligence documents from the bodies of the dead officers.
That morning, Breen had been unhappy about the journey, telling his staff officer, sergeant Alan Mains, he suspected the IRA had a source in Dundalk garda station.
Buchanan, a born-again Christian, took the view that his life was in God's hands. That may explain why he felt comfortable driving his own car to scheduled meetings in Dundalk, often parking it in front of the station where it was visible from the road.
During the meeting in Nolan's office, a vehicle was observed by gardai driving slowly through this parking strip. The driver was looking around. Another car drove slowly past the station three times. It looked suspicious, but nobody did anything about it.
Eleven years ago, Jeffrey Donaldson, then an Ulster Unionist MP, used parliamentary privilege to allege that detective sergeant Owen Corrigan had passed information to the IRA. Corrigan, now retired, has always denied this.
Two years ago, his libel action against the Mail on Sunday was settled, with the newspaper publicly withdrawing the allegation and stating that it was false.
McBurney believes there could have been a tip-off but it "was not a vital component" of the IRA operation. This particular meeting was arranged at short notice but the practice of holding meetings in border stations, often Dundalk, could have led to IRA surveillance of the car park, which was visible from the road. A second car park at the back of Dundalk station was also visible through a large set of gates.
McBurney believes the officers should have travelled by helicopter to Dublin or Belfast instead of driving to Dundalk in Buchanan's car without police or military cover. He wants to see what security assessments were carried out by the Irish and British governments, but fears that a new time limit put on the tribunal by the Irish government will lead to it focusing purely on what happened on the day of the attack. "The assessment that I think needed to be carried out would be a joint assessment by police and army with an intelligence dimension from army intelligence, Special Branch, and MI5," he said.
The lawyer also wants to see all intelligence reports from Stakeknife, the British army's top agent within the IRA who was often in South Armagh in his role as head of the Provisionals' counter-intelligence unit. The suspicion is that Stakeknife may have handled one or more gardai for the IRA, or at least been aware of their role, and informed his own handlers in the British army of this, who failed to act on the information in order to protect his cover.
There is also suspicion over Stakeknife's possible role in the interrogation and murder of Tom Oliver, a Co Louth farmer killed by the IRA for allegedly passing information to the gardai in 1991.
Ian Hurst, a former member of the Force Research Unit which controlled Stakeknife and who has co-written a book on the agent, says he wants to give evidence to the Smithwick tribunal. However Hurst, whose story was told under the pseudonym Martin Ingram in The Sunday Times in 1999, says: "I am effectively prevented from helping the tribunal by the [British] Ministry of Defence who refuse to vary an injunction forbidding me to disclose many aspects of my military career."
This is one reason why Justice Smithwick's inquiry has taken almost six years to prepare and will finally open on June 7. Much of the information the inquiry chairman needs is in Britain, and it has not always been easy, or even possible, to get hold of it.
The tribunal opens at a moment of acute "inquiry fatigue" on both sides of the border. The Moriarty and Mahon tribunals in the south, and several Troubles-related inquiries in the north, have involved cost and time that many believe are out of proportion to what they found.
A judicial tribunal into the murder of the solicitor Rosemary Nelson ended last week, having cost £46.5m (€53.7m), largely duplicated the findings of an earlier report by the police ombudsman, and making no recommendations at all.
The idea that a public judicial inquiry represents the gold standard when it comes to uncovering the truth has been badly discredited. If the Smithwick tribunal is curtailed, the allegations won't go away.
There will be calls for a more cost-effective and holistic truth-recovery process, perhaps conducted by an international panel of investigators with the power to requisition secret material, interview undercover operatives, and make public as much information as possible afterwards.
