A gang of teenage arsonists shut the M1 for nearly a week when they set fire to a scrap yard under the motorway and caused £4.5 million worth of damage, a court heard.

The blaze caused misery for thousands and came at the end of a five-day firestarting spree, it was alleged. The flames engulfed the scrap yard, an industrial unit and the flyover leaving it “charred and damaged”.

Johno Johnson, 18, Josh Lambe, 18, Luke Matthews, 18, a 17-year-old and two 15-year-olds, who cannot be named for legal reasons, all deny conspiracy to commit arson at the scrap yard on Ellesmere Avenue footpath underneath the M1 flyover belonging to Terry Mizon on April 15 last year.

James Brown, prosecuting, said: "This offence became notorious because as a result of what these defendants did, setting fire to a scrap yard underneath the M1 motorway at Apex corner.

"There was an enormous conflagration of flames to such an extent that the fire spread from that location to another industrial complex next door and it was such an enormous fire that it actually structurally damaged the flyover of the M1 and the motorway was closed for nearly a week and the cost of repair to that main artery road was £4.5m."

Opening the case at Wood Green Crown Court Mr Brown added: "It was in fact one of a series of arsons that these defendants perpetrated.

"It was different in the sense that the scale of damage caused was different from the other offences but similar in that it was also an agreement to gratuitously destroy other peoples property.

"They set the fire in the scrap yard and to use the old expression 'you pay your money and you take your chance'. If you start a fire in a scrap yard full of combustible objects and scrap anything could happen.

"What did happen was about as bad as anyone could envisage in terms of the damage caused."

The arson spree began on April 12 when the group set fire to a Wendy House in Edgewarebury park, north London, before returning the next night to burn a play unit, it is alleged.

Then in the early hours of April 15 they set fire to a picnic shelter In Moat Mount open space, Mill Hill before some walked to Apex metals and set fire to the scrap yard just before 4am where the blaze became “intense” because of the presence of gas cannisters.

On April 16 they returned to Mill Hill and set a second picnic shelter ablaze, it is alleged.

Mr Brown said: “It is the Crown's case that this is a spree of arson that took place involving these defendants over a five day period.”

Of the six accused of the M1 fire charge, Lambe denies one of the Mill Hill fires and the later Edgewarebury park fire, but admits the one that was started earlier that evening. One of the 15-year-olds denies one of the conspiracies at Mill Hill and one at Edgewarebury park, but admits one of the conspiracies at each location and the other 15-year-old, from Harrow, denies three charges of conspiracy relating to all the fires which took place before the M1 fire.

Matthews, of Hatfield, Johnson and the 17-year-old all admit all four other conspiracies to commit arson apart from the M1 fire.

Accused of involvement in fires not including the M1 blaze, a 14-year-old denies one of the Edgewarebury park fires and 18-year-old Damien McQueen denies both conspiracies relating to the fires in Edgewarebury park.

Hannah Parker, 18, denies conspiracy to commit arson relating to the two fires in Mill Hill and Jaun Durandt, 18, has admitted the conspiracy relating to the earlier Mill Hill fire but denies the second. Apart from Matthews, of Hatfield, and one of the 15-year-olds, from Harrow, all of the defendants are from Edgware and they all live in the “same geographical area” as their trail of fires.

Pictures and videos of all the fires but the M1 blaze were taken on Johnson's mobile phone and have been recovered by police.

Mr Brown told the jury that the defendants between them face five charges of conspiracy to commit arson meaning the one who lit the blaze was irrelevant as long as they were sure there was an agreement.

The trial continues.