The most seriously injured 7/7 survivor told today how he saw Mohammad Sidique Khan detonate the Edgware Road bomb.

Daniel Biddle, 31, described seeing Khan's arm move quickly to a white cord on or in his rucksack. "Then there was a big white flash and the kind of noise you get when you tune the radio in," he told the inquest into the 2005 bombings at the High Court.

"It just felt like the carriage I was in expanded at a fast rate and then contracted quickly and with that it blew me off my feet through the carriage door and into the tunnel."

He was within six feet of the blast and lost both legs, his spleen and his left eye. He needed 87 pints of blood to recover and was in a coma for five weeks.

Mr Biddle said a 20p piece remains lodged in his thigh bone and other shrapnel, including his door keys, were removed by surgeons.

He said he was only on the train with Khan because he had been fiddling with his mobile phone and missed his intended stop. He was also running later than usual for his job as a project manager on a building site partly because he had a migraine. Today he told the hearing how he saw Khan get on the train at King's Cross. "There was nothing about him that made me think he was a danger in any way," he said.

"He was holding a small black camping rucksack and I remember it being on his lap."

As the train pulled out of Edgware Road station Mr Biddle was looking at the Tube map but he noticed Khan moving his arm and the rucksack still on his lap. "He looked up and along the carriage and then he just looked down," Mr Biddle said.

"He didn't say anything, he didn't shout anything that I can remember hearing. He just put his head down, moved his arm and the next thing I remember I was outside the train."

Mr Biddle found himself lying next to one of his legs which had been blown off and another body on the tracks.

Two men came to his aid to try to move a huge lump of metal, probably the train door, off his body. One told Mr Biddle to hold the other man's hand. When Mr Biddle asked why he was told: "It's going to f***ing hurt."

There was further laughter in court when Mr Biddle said that on his way to St Mary's Hospital the ambulance driver hit the kerb and was abused for his clumsy driving.

The coroner Lady Justice Hallett today praised Tube passenger Adrian Heili, who held Mr Biddle's femal artery between his thumb and forefinger in the crucial minutes after the explosion. He also ripped up his own shirt for tourniquets for the victim's legs and bandages for his head wounds.

Mr Heili, a South African who trained as a medic in the Austrian Army, went on to help up to 10 other passengers. He was awarded the Queen's Commemoration for Bravery.

Lady Justice Hallett said: "Your fellow passengers were extremely fortunate to have you there that day. You were cool, calm, collected and courageous. I don't believe the brave Mr Biddle would have survived his injuries but for your intervention."

The case continues.