By Kevin Connolly BBC Ireland correspondent

Like all the best stories about spies and spying it combines elements of the sinister and the absurd.

A huge, heavily-guarded security base is effortlessly penetrated by a three-man gang who find their way without difficulty to a Special Branch office somewhere in the labyrinth of corridors and stairways.

It would be naive to assume that the truth will emerge quickly, if at all

They overpower the one junior officer working the Sunday evening shift on St Patrick's day in an office which was in effect the engine-room in the British intelligence community's war against paramilitary violence in Northern Ireland.

They spend perhaps 20 minutes ransacking the office and escape with a number of documents.

They escape again without being detected, leaving in their wake a sense of shock that what should be one of Britain's most secure buildings was so easily burgled, and apprehension about how the papers they stole might be used.

Inquiries begin

Already, there are two inquiries under way - one by former Northern Ireland Office Permanent Secretary Sir John Chilcot who was commissioned by the Northern Ireland Secretary, Dr John Reid and one by the police themselves. If investigations suggest the involvement of serving officer, the Police Ombudsman may later hold another investigation.

Even with all that going on though, it would be naive to assume that the truth will emerge quickly, if at all.

In the murky world where overlapping networks of informers report to the police, to the army's intelligence service and to MI5, conspiracy theories abound, and concrete facts are something of a rarity.

Sir Ronnie Flanagan: No informants were identified

It seems unlikely that a paramilitary organisation like the IRA was behind the operation, if only because the robbers moved into and around Castlereagh so easily that it is thought they must either work for the security themselves - or have help from someone who does.

That leaves the possibility that one intelligence agency is out to embarrass another - not at all an unlikely scenario in a world where budgets and areas of responsibility are keenly fought over.

It is also possible that a rival agency was hoping to frustrate enquiries into past operations by stealing documents which might prove to be incriminating.

Rogue officers hoping to destroy evidence of their own wrong-doing are also among the list of possible suspects.

In truth, no-one knows.

Answers sought

Clearly embarrassed by what is perhaps the worst breach of security of its kind in recent times, the outgoing chief constable of the Police Service of Northern Ireland Sir Ronnie Flanagan will only say that the documents which were stolen will not help whoever stole them to identify individual informers.

We do not know enough to adjudicate between the rival theories, just enough to suggest that definitive answers will be hard to come by.

It is about 12 years since someone broke into the offices of the Stevens inquiry team in a police station in Northern Ireland and started a fire at the height of their investigation into alleged collusion between members of the security services and loyalist paramilitaries.

More than a decade later, we are still waiting for answers to who carried out that attack, and why they did it.

We should not assume that answers will come any more quickly this time around.