The suicide bus bomber Hasib Hussain made frantic telephone calls to his fellow bombers minutes after they blew themselves up on London underground trains on July 7, it emerged last night.
Hussain, 18, tried to call his accomplices at around 9am, but none answered because they had already killed themselves and 39 other people in their almost simultaneous attacks at 8.50am.
He finally set off his own bomb, 57 minutes later, on board a number 30 bus to Hackney, killing 13 people.
It is thought that Hussain, from Holbeck in Leeds, was supposed to detonate his rucksack device on a Northern line train at the same time as his three fellow suicide bombers travelled south, east and west.
However, he did not get on the train, and it is unclear whether this was because there was a problem with the line at that time, or for some other reason.
Police have tried to piece together the missing hour from when Hussain left his accomplices at King's Cross station to when he murdered the passengers on the bus at Tavistock Square.
Police officers watching hours of CCTV footage now believe that Hussain left King's Cross station to get a signal for his mobile phone to call the others. He is then seen going to a McDonald's restaurant nearby, according to the Independent newspaper.
He had travelled from Luton to King's Cross that morning with Mohammad Sidique Khan, Shehzad Tanweer and Germaine Lindsay and police were concerned that he may have met a terrorist mastermind or other members of a wider network during the missing hour.
A terrorism expert, Michael Clarke, of King's College London, told the BBC that the calls showed that Hussain was in a panic and probably rang his accomplices to make sure their bombs had exploded.
The attempted calls could suggest that Hussain's panic was brought about because he was unsure of what to do after failing to get on the Northern line train, which in turn would provide evidence that the bus was not the intended target on the morning of the attacks.
This undermines the theory that the July 21 attempted attacks in the capital were linked, and indicates that they were more likely to be a copycat strike.
It is known that the July 7 suicide bombers triggered their rucksack bombs themselves by pressing a device similar to a button. Detectives say this rules out theories that the men were duped into the suicide bombings.
The devices associated with the failed attacks two weeks later were also to be manually detonated, it was claimed.
Earlier it had been suggested that mobile phone timers may have been used for detonation, a method deployed in the Madrid commuter train bombings.
This breakthrough, more than six weeks since the attacks, provides police with potentially important clues about the bombers' planning and technical knowhow.
A total of 52 innocent people were killed in the July 7 bombings. However, no one is currently in custody in connection with the attacks that day, nor has anyone been charged.
So far 14 people have been charged in connection with the July 21 attempted attacks.