The raid that brought down a government

The initial response of John Reid, the Secretary of State for Northern Ireland, to the sight of dozens of burly policemen milling around in Sinn Fein's Stormont offices was, it is said, a salty Glasgow oath.

The reaction of the Northern Ireland Chief Constable, Hugh Orde, to the same TV pictures is believed to have been framed in similarly earthy language.

The minister and the policeman both realised instantly that the power of the images had the capacity to cause immense disruption to the province's politics.

So it has proved, with the power-sharing executive at Stormont due to be placed in suspension from midnight tomorrow. The episode has led to allegations that anti-republican elements conspired to ensure that events were as damaging as possible to Sinn Fein.

The saga began when a junior official at Castle Buildings, which houses Mr Reid's offices, was discovered at a photocopier in September 2001. He denied wrongdoing and was shifted to a less sensitive department.

He had been vetted before being employed, and again he was vetted and pronounced "clean". Mr Reid was told last spring that an investigation was taking place, and he was recently informed that inquiries were continuing. He was not told that offices at Stormont, Northern Ireland's seat of government, were to be raided.

Meanwhile, Mr Orde was briefed on the inquiry after moving from the Metropolitan Police to Belfast at the beginning of September. He knew that searches and arrests were planned. But when he flew to London on police business, he had not been told of any plan to mount a search at Stormont.

Searching the offices of a political party was sensitive enough, but a formidable force was deployed in a fleet of armoured Land Rovers. Nineteen officers, armed and wearing flame-retardant overalls, took away two computer disks, making no attempt to remove hard drives, on which much more information can be stored. The fact that the search took place in front of television crews gave the exercise worldwide interest.

The widespread feeling that this was excessive was acknowledged by Mr Orde when he made a public apology for the way that the search had been carried out.

He said later: "There was no pre-planning in relation to the issues around Stormont. At the time of the arrests, the plan was not to carry out other searches."

The effect of the operation was to trigger a crisis that is about to bring down the executive in a manner that directs most of the immediate blame at Sinn Fein.

Few doubt that republicans have been involved in political espionage. But questions remain about an investigation that ran for 13 months, culminated in a search of a political party's offices at a most sensitive time and brought down a government.