The IRA had planned to knock out the power supply to the southeast England in the final years of its terror campaign, a former member has claimed.
It is alleged the plan would have taken place in the mid-1990s, shortly before the Belfast Agreement peace accord.
Former US Marine turned IRA gun runner John Crawley made the claim in the final episode of the BBC series 'Spotlight on the Troubles: A Secret History'.
The IRA broke its 1994 ceasefire in February 1996 when it exploded a bomb in London's docklands, which killed two people and caused an estimated £150 million worth of damage.
In June that year, the IRA exploded what was reported as the largest bomb to be planted in Great Britain since the Second World War.
More than 200 people were injured in the blast in Manchester and there was significant damage to infrastructure.
The bombs came as Sinn Féin was at loggerheads with the UK Government and unionists over calls for the IRA to disarm before the Irish republican party would be admitted to peace talks.
The BBC programme hears claims that the key IRA bombers had been either caught or killed after extensive surveillance operations by police and MI5.
John Crawley, who had previously been caught smuggling guns from the United States for the IRA, told the programme how he was arrested just before a plan to bomb London's electricity supply was carried out.
"We were going to knock out the power supply of the southeast of England."
"And there may have been other operations after that, but we were caught before we could do that," he told the programme.
John Grieve, who took over Scotland Yard's anti-terror unit on the day of the Canary Wharf bomb, described Mr Crawley and the other IRA bombers as "the A team".
"They were absolutely excellent and one of them, John Crawley, ex-US Marine Corps demolition specialist, this was the top sort of people for them to bring up.
"He just epitomised the cunning, skills, experience, of the sort of people they were putting against us," he told the programme.
But Mr Crawley revealed the IRA had been left overstretched by the campaign.
"I wondered why they didn't kill us, because we'd have had men tooled up and everything," he said.
"They knew where we were going and to this day, I don't know why they just didn't take us out of it.
"Because coffins coming back on the ferry would've been a nice message to anybody else looking to go.
"And believe me, there wasn't a lot of people putting their hands up to go to England."