IT IS what Guy Fawkes would have wanted. Four centuries after the most famous non-explosion in history, a documentary team has spent £1 million blowing up a replica Parliament.

ITV1 staged the pyrotechnics to see what would have happened if Fawkes and his fellow Roman Catholic conspirators had evaded detection and the Gunpowder Plot had succeeded.

Explosives experts built a full-size replica of the then Palace of Westminster on an MoD-owned testing site in Cumbria and packed 36 barrels with a tonne of gunpowder.

The results suggest that the impact of the blast would indeed have wiped out Britain’s elite if Fawkes had ignited the fuse 400 years ago this week.

Historians have previously suggested that the attempt would have failed. An examination of the gunpowder seized when the plot was discovered showed that it had decayed because of a month’s delay caused by plague before the 1605 State Opening of Parliament.

Working with blast consultants from engineering giant Arup, the producers of The Gunpowder Plot: Exploding the Legend sourced gunpowder closest to Fawkes’s compounds of saltpetre, charcoal and sulphur from a factory in Spain. Using 650 tonnes of concrete and based on archive plans, the undercroft where the gunpowder was hidden was recreated and the full Lords chamber built above. It was packed with perishable cameras, sensors and crash-test dummies to represent King James I and the 150 bishops, members of Parliament and noblemen present. A spectacular explosion ensued.

Unlike Fawkes, who planned to ignite the gunpowder with a cotton rope boiled in saltpetre, the ITV team pressed a red button in a control room connected by cable to the replica 750m (2,461ft) away.

The result, screened tomorrow, claims to prove that Fawkes’s plot would have propelled the timber floor of the Lords upwards with such violence that King James I and everyone else in the chamber would have been killed.

Arup, the engineering company that carried out the explosion for the show, said: “Any of the other physical effects of the explosion, such as direct blast pressure, scorching, impact of high-speed timber fragments and the impact of falling back down to the ground could also have killed many, if not all, of those present. But the extreme upward thrust would have been the primary cause of death.”

Tests carried out by Sidney Alford, the programme’s explosives consultant, showed that decayed powder does explode.

If Fawkes had lit the fuse, the powder would have blown — and he had twice the powder needed to destroy Parliament utterly.

Contrary to previous claims, the blast would have been relatively contained, with Parliament’s 1.8m-thick stone walls directing much of the pressure of the blast upwards.

The debris from the roof and floor of the chamber blown upwards would have rained down in a 200m radius. Experts also concluded that the blast could have been heard at least five miles away.

David Hadden, Arup’s blast consultant, said: “After years of speculation, the test has proved once and for all that Fawkes’ plan would have had devastating consequences for anyone present in the House of Lords that day, though not for the surrounding areas as previously thought.”

The Gunpowder Plot: Exploding the Legend — tomorrow, ITV1, 9.45pm

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