MR John Major yesterday welcomed a spectacular triumph for MI5 and the anti terrorist squad in the fight against the IRA, but the mood of congratulation was tempered by terrorism expert Prof Paul Rodgers, who forecast an early resumption of IRA attacks in Britain.
The British prime minister said he was delighted at the success of the raids - which yielded the equivalent of five Manchester style bombs, two lorries and other vehicles, booby trap devices and assassination kit.
The finds appear to blow a hole in recent speculation that a renewed IRA ceasefire is possible. In London last night senior politicians and security officers were again questioning the authority and intentions of the present republican leadership - given the potentially devastating implications of the discovery for Sinn Fein's relationship with the Clinton administration and the certainty of renewed unionist demands for decommissioning as a precondition to the party's entry to the talks process.
Metropolitan Police Commissioner Sir Paul Condon said they had "frustrated an attempt by the Provisional IRA to carry out significant attacks . . . with the possibility, indeed probability, of grave loss of life and massive disruption". He made it clear that the "imminent" IRA attacks could have occurred as early as yesterday or today.
Despite obvious and immediate speculation, the Commissioner said the finds were not being specifically linked to the party conference season, which got under way yesterday with the Liberal Democrat assembly in Brighton. Labour meets next week in Blackpool, ahead of the Conservative conference in Bournemouth the following week.
Assistant Commissioner Mr David Veness, who has responsibility for Scotland Yard's specialist operations, said the homemade explosives were virtually "ready for use" and would probably have been used as large vehicle bombs, similar to that which injured 200 people in Manchester in June and the one which killed two people in London's Docklands last February.
As well as planned "spectaculars", the possibility was raised that the escalating IRA campaign may have included attempts on the lives of prominent politicians. Mr Veness revealed that the haul included at least two devices which he described as "under car booby traps" which were "to be placed under cars with the intention of causing death and grave injuries".
Reacting swiftly to the seizures, Mr Major said: "I am absolutely delighted by the success of the security authorities in foiling the IRA's latest plans to attack the people of this country as they go about their daily lives. The police and the security service deserve all our congratulations for this important operation."
Addressing the political implications of the foiled IRA mission, the prime minister said: "The discovery of these plans, and the huge stocks of explosives arms, put in their proper context professions of peaceful intentions by Sinn Fein's leaders and speculation about a new IRA ceasefire. It remains impossible to reconcile Sinn Fein's rhetoric for peace with the IRA's preparations for murder."
He continued: "The British government remains fully committed to the Belfast negotiations aimed at a comprehensive political settlement in Northern Ireland. Northern Ireland's future will be settled by democratic, peaceful discussion, not by violence or threats of violence. It is time Sinn Fein and the IRA learned that lesson once and for all."
Prof Rodgers, of Bradford University, echoed the view that the discovery of such large quantities of explosives and bomb making equipment showed there was no immediate prospect of another ceasefire. He suggested the finds might set back the IRA campaign by some months. But while they represented "a considerable success" for the authorities, he said they confirmed the IRA was stepping up its campaign in Britain.
Suggesting that a smaller "calling card" could be expected from the IRA within the next few weeks - to demonstrate it had not been beaten by the second reversal in three months - the professor said: "We are in an era of pretty major IRA activity. It is good news that the explosives and bomb making equipment were found, but bad news that they were there in the first place."
The Tanaiste, Mr Spring, who is in New York attending the United Nations General Assembly, said that the IRA activity in London uncovered by the police "would appear to be totally inconsistent with those in Sinn Fein advocating a peace strategy. Such IRA action undermined the peace process in Northern Ireland, he said. "It has to be condemned in the most outright and straight forward terms."
Meanwhile, a White House spokesman congratulated the British authorities for "good police work" and urged the IRA to restore its ceasefire immediately.