Manfo Asiedu was supposed to have exploded his rucksack device in the failed 2005 bomb attack but lost his nerve at the last moment, dumping it in woodland near Little Wormwood Scrubs.

Ghanaian-born Asiedu, of no fixed address, has pleaded guilty to conspiracy to cause explosions of a nature likely to endanger life between March and July 2005.

Opening the case against him at Kingston Crown Court, Nigel Sweeney QC, prosecuting, said: "The defendant's principal role in the conspiracy was in the purchase of 443 litres of hydrogen peroxide, or 110 gallons in old money, which were a vital ingredient in the main charge of the explosive devices required to be connected."

Before July 21 he knew that the would-be suicide bombers were extremists who were planning an attack and even helped make up the home-made devices, the court was told.

He lived in a one-bedroom flat, turned into a bomb-making factory in New Southgate, north London, with some of the men now convicted in connection with the attack and was in telephone contact with them.

"Further he took part in a cover-up after the bombs failed to explode both for his benefit and the benefit of his conspirators," Mr Sweeney said.