So do we know now why the Director of Public Prosecutions, the Attorney General and the Northern Ireland secretary were so desperate to stonewall after the collapse of the "Stormontgate" court case?
Clearly, none of the above would have relished the unmasking of the veteran republican Denis Donaldson as an equally veteran British agent.
His exposure would not have been considered in the "public interest".
There are reports that other informants may have been involved in Stormontgate.
Denis Donaldson admitted being a British agent
Either way, protecting such a highly placed agent as Denis Donaldson would have been high on the authorities' agenda.
Both the DUP and the Ulster Unionists have called for a public inquiry.
But is a government so reluctant to expand on the reasons behind dropping the Stormongate charges going to concede a public inquiry into such a sensitive area?
The Alliance Party has also joined the chorus in support of a judicial inquiry, but their justice spokesman, Stephen Farry, says that those politicians who have demanded that such a probe should be held in public are demonstrating "the height of naivety and irresponsibility".
Whether or not there is an inquiry, a mass of legitimate questions arise.
Was Denis Donaldson an informer reporting back to the police and British intelligence on espionage carried out and authorised by other republicans?
Or was he - as Sinn Fein argue - acting as an agent provocateur creating - in his words - a "sham" IRA spy ring?
Given Denis Donaldson's long service as a British agent what prior knowledge did the police have not just of Stormontgate but also of the raid on Castlereagh police station in March 2002?
It's generally been understood that in response to that raid the police ran an operation codenamed "Torsion" which led to the Stormontage arrests in October 2002.
But in court, the prosecution made much of Denis Donaldson's links with Larry Zaitschek, an American suspect whose extradition has been sought in relation to the Castlereagh raid.
Police raided Sinn Fein offices at Stormont in October 2002
So did the agent know about Castlereagh before it happened and what did he tell his handlers?
Then there's the £30m or more spent on relocating security force members and prison officers whose personal details were compromised. Were they ever really under threat?
All of these operational matters serve as a prelude to the broader political questions. Stormontgate hastened the end of the power sharing executive in October 2002.
David Trimble famously dubbed the affair "worse than Watergate".
But if the spying allegations were bogus, was the fall of the government manufactured by "securocrats", as republicans suggest?
Would the authorities have gone to such lengths to topple an executive which looked pretty doomed at that stage anyway, albeit that the scandal switched any blame from unionists to republicans?
Any inquiry, whether in public or in camera, would have plenty of cud to chew on.
But it's hard to envisage any probe exposing a version of the truth which will satisfy the participants in the political process.
As they head into a New Year when London and Dublin were promising to intensify their efforts to broker a deal, the politicians can only know one thing for certain, namely that Northern Ireland's dirty war has been succeeded by an equally dirty peace.