The British and Irish governments are convinced that the £26m (€37.5m) heist was carried out by the IRA because of a briefing from Hugh Orde, the PSNI chief constable, in which he gave the names of the suspects. Both the PSNI and gardai observed meetings between republicans they suspect planned the robbery and senior Sinn Fein figures, including Gerry Adams.

Security sources will not give details of these meetings, although they coincided with negotiations last month between the governments and Sinn Fein on a complete end to IRA activity. “It is reminiscent of the 1996 negotiations during which the Canary Wharf bombing was being planned,” one British source said.

The PSNI has studied reports from informants, tapes taken from listening devices and telephone taps that indicate IRA involvement. In a briefing, the chief constable said that intelligence gathered before the robbery gained new significance when viewed with the benefit of hindsight and left him in no doubt as to who was involved.

On the basis of this analysis, and of fresh intelligence gathered since the robbery, police have briefed the two governments that it was carried out by the Provisional IRA as an organisation. They have ruled out the heist being the work of a faction or a collection of disgruntled individuals.

It is said to have been sanctioned in detail by the IRA’s general headquarters staff, and that the IRA army council is believed to have been aware that a huge robbery was to occur close to Christmas. Both Adams and Martin McGuinness have been accused under parliamentary privilege of membership of the IRA army council and, though the Sinn Fein MPs deny it, police believe they are members.

The governments have been told that the robbery was organised by the Belfast brigade of the IRA with support from other areas, including south Armagh. Southern command, based in the republic, supplied the van used to transport the cash to premises in west Belfast, where it was moved to other vehicles before being transported to south Armagh and north Louth.

The adjutant of the Belfast brigade of the IRA, a relative and friend of Adams, is believed by police to have taken part in the heist along with John Trainor, the intelligence officer of the Belfast brigade. Both men’s houses were raided, along with the home of Eddie Copeland, a senior north Belfast republican, after the robbery.

Police have said the raids were not speculative but based on intelligence. They are confident their operations could be justified if there was an inquiry by the police ombudsman.

Bobby Storey, named in parliament as the IRA’s most senior intelligence officer and a planner of the robbery, is another close Adams associate. Storey was instrumental in quashing dissident opposition to the peace process and is regarded by the police as the brains behind the raid on Special Branch headquarters in Castlereagh. He is also believed to have planned other robberies, including one that netted more than £1m at Makro retail centre in Dunmurry last year.

The Independent Monitoring Commission (IMC), which monitors paramilitary ceasefires on behalf of the two governments, is expected to recommend sanctions against Sinn Fein in a report within the next fortnight. The IMC met last week and was given much of the police’s intelligence.

Possible sanctions against Sinn Fein include the ending of government support, such as the money paid to the party in allowances at Westminster and the Dail, and suspension from public office for up to a year.

Last April, following the IRA’s abduction of Bobby Tohill in Belfast, an IMC report recommended the suspension of some Northern Ireland assembly allowances. This has cost Sinn Fein £120,000 and last week it challenged the decision in the High Court in Belfast.

A verdict may be delivered this week.

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