The IRA's truck bomb was driven to London from Northern Ireland with false plates and a tax disc stolen in the province three weeks ago, the Rev Ian Paisley told the Commons yesterday.
He said the lorry used in the attack had been taken to London by ferry from the Co Antrim port of Larne across to Stranraer in Scotland. The Democratic Unionist leader said the details had been confirmed to a constituent of his - the person who lost the tax disc - by police.
Mr Paisley's son, Ian Junior - the Democratic Unionist Party justice spokesman - said in Belfast that the tax disc had been taken from a lorry on the forecourt of a car salesman's property in his father's North Antrim constituency.
"It was a second-hand English registered vehicle," he said and added: "It was stolen three weeks ago - before the Mitchell Report [on arms decommissioning] was even completed."
Mr Paisley Jnr said the dealer had told the RUC but put the theft down as "one of those things". He said the dealer thought no more of it but realised what had happened when the Metropolitan Police had the registration number of the bomb lorry read out on television and radio.
Neither the Metropolitan Police nor the RUC in Belfast would comment on Mr Paisley's claim but the Prime Minister, in responding to the Democratic Unionist Party leader, described the tax disc as "very strong corroborating evidence".
IRA attacks in England have often showed evidence of being planned for months rather than weeks. In the case of the Docklands attack, it is likely that many weeks were needed for the selection of a target, the choice of a precise location, and the preparation of the lorry used.
News that the Docklands bomb had been at least three weeks in the making raised questions about the apparent failure of the security and intelligence services to predict the sudden and dramatic end of the peace process.
The last formal assessment at the end of January, and sent to all police forces, was that the threat of terrorist attack was "low".
Some police officers yesterday were quick to seize on the disaster to accuse MI5 of being distracted from its anti-terrorist role by its efforts to play a leading role in the fight against crime.
But government sources insisted yesterday that Ministers were content with the advice and assessments they had been given, stressing that intelligence both north and south of the Irish borders had also failed to penetrate the most senior ranks of the IRA.
Last night it was clear that the security services and Special Branch were aware of an increase in IRA movement and "tensions" but said one: "Clearly the timing took everybody by surprise".
Meanwhile, police in London were following up dozens of leads from callers responding to the details and impression of the bomb truck, released by Scotland Yard on Sunday. Detectives will be trying to piece together its journey from Larne down into London Docklands on the fatal Friday.
Yesterday officers were studying hours of video evidence taken from the numerous security cameras in the Docklands area to help identify the bombers.
A police spokeswoman would give no details of evidence they had so far gathered but said that they were pleased with the response and were making steady progress. Forensic experts, meanwhile, continued their painstaking search for clues through the rubble of South Quay, while divers searched the murky waters of the neighbouring docks.
Sir Paul Condon, the Metropolitan Police Commissioner, repeated warnings that the IRA could well carry out a second attack. Urging people to return to their pre-ceasefire vigilance, Sir Paul said: "Following the tragedy of the bomb at Canary Wharf, Londoners must now face the possibilities of further bomb attacks in London and be as prepared as we can for such criminal attacks on our great capital city."
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