Some now suspect that the Castlereagh raid was carried out in an effort to discredit the PSNI's Special Branch, writes Jim Cusack, Security Editor
One of the expected developments which, it was assumed, would immediately flow from the break-in at the PSNI's office was the disappearance of terrorist informants from Northern Ireland. The office handles agent intelligence.
On any previous occasion when an informant's identity had been compromised he or she was swiftly taken from their home by police or the British army, given a new identity and set up in a new location with a new life. These events are immediately known about in the organisations and tight-knit areas where the informant worked.
Compromised informants are targets for assassination by the terrorist group which they infiltrated. This applies whether or not a ceasefire is in place.
Sources in both the security forces and paramilitaries are describing as remarkable the fact that no informant appears to have felt their life was sufficiently threatened by the Castlereagh break-in to flee.
Another unusual feature of the break-in was that the three men who carried it out used "prisoner handling" techniques which were perfected by the RUC's E4 Department.
The Special Branch duty officer in the Castlereagh office was overpowered, made to kneel and then had one foot place over the other ankle before being bound by plastic ties identical to those used by the police and military.
While office cabinets were being searched, one of the raiders checked on the bound man's hands and feet to make sure he was not suffering circulatory problems. His pulse was also checked.
Sources in the security forces and the paramilitary world say it would be unlikely that an IRA unit would be trained in these techniques or be sufficiently bothered with the bound man's welfare to take time to check on his well-being.
The raiders also had a good knowledge of the layout of the Castlereagh complex, which is undergoing extensive renovation. The Special Branch office, known as 220 after the telephone extension used to contact it, had moved less than two weeks earlier as part of the renovation.
An unusual feature that tends to point away from paramilitary involvement in the raid is that the raiders ignored several weapons that were kept in the same office.
The CID investigators quickly established from electronic surveillance of senior IRA figures that the IRA had the documents. The homes of several leading republicans were subsequently raided but no evidence was found.
The exact nature of the documents taken by the raiders remains uncertain. However, it is known that a list of Special Branch officers' names and home telephone numbers was taken. This has led to several officers and their families moving home and being resettled elsewhere because their security was compromised.
Some sources now point out that the break-in came at a crucial point in the peace process. Sources within the Special Branch believe the raid was mounted by another security agency, either the British army or UK domestic intelligence agency, MI5, and the documents then passed to the IRA.
The reasoning behind this is that it would discredit what remains of the old RUC Special Branch and speed up the process of it being amalgamated under the CID Branch - in other words, the effective disbandment of the Special Branch. The disbandment of the Special Branch is one of the key demands made by Sinn Féin in its negotiations about joining the Northern Ireland Police Board.