The most seriously injured survivor of the July 7 bombings today described the moment in which he watched bomber Mohammed Sidique Khan detonate his device just feet away from him, killing six people.

Daniel Biddle, 31, was so severely injured in the Edgware Road blast that he lost both legs, his left eye and his spleen. Today he told the inquests into the 52 people who died that he had been standing no more than six feet from where Khan was sitting when he noticed the bomber making a movement with his arm in his rucksack, possibly pulling a white cord, which set off the device.

"He didn't say anything, he didn't shout anything that I can remember hearing. He just looked down the carriage [and] made his arm movement," Biddle said.

There followed a "big white flash" and "the kind of noise you get when you turn a radio on, that white noise. It felt like the carriage I was in expanded at a fast rate and then contracted quickly."

Biddle was flung out of the train and onto the narrow gap between the carriage and the tunnel wall.

He had smacked his head and had a large piece of metal debris positioned over his legs, he told the inquests, presided over by coroner Lady Justice Hallett.

"As I was trying to move myself around I had something digging into my back," he said. "I repositioned my shoulders, reached behind me and pulled out that much of a leg and foot."

He could see several bodies, he told the coroner, one as little as 2ft away. "I was terrified, seeing what I had seen, and thought I was going to die. So I was screaming just as loud as I could to get help."

The inquests heard that Biddle's commute from Romford had been delayed by a migraine that morning and by a broken ticket machine. Lady Justice Hallett told him: "The words 'if only' must resonate in the minds of so many survivors and families. Given the large number of factors that combined to put you on that train, I pray they do not haunt you.

"You have suffered so much and your survival is inspirational."

Biddle told the court that doctors had removed from his body his door keys and "about £7.40 worth of pound coins and 10p and 20p pieces, and I have a 20p piece lost in my thigh bone still."

One of those who came to Biddle's aid was Adrian Heili, a former soldier in the Austrian army who was trained in first aid and had been travelling in the carriage behind.

He told the inquests he heard Biddle screaming and shouted out of the train to him before making his way to the rear and then back to where the injured man was lying. To do so, he had passed the badly burned body of a young woman on the tracks, he said.

He said the decision to leave her and proceed to those he might be able to save was "the hardest decision I have had to make".

Heili said he climbed under the train to reach Biddle, through a pool of "thick liquid, which I later attuned was blood".

"I noticed that Mr Biddle was missing a leg, there was also blood coming out of his femoral artery which I closed with my thumb and forefinger," he told the coroner. He had used his own belt as a tourniquet and had ripped up his shirt to tie around Biddle's other leg, which was so severely damaged that the foot was being held on only by tendons and skin, he said.

Once a paramedic arrived, some 25 minutes after the blast, Heili said he had helped him to insert an IV line before making the short trip along the tunnel to Edgware Road to get a stretcher on which Biddle could be evacuated.

After helping to carry Biddle from the scene, Heili said he returned to the bombed carriage where he had seen bodies and "fragments of bodies" spread throughout the carriage. He had moved a number of the dead to clear a passage for the wounded and for paramedics.

He said he had made repeated trips, escorting between eight and 10 walking wounded to the platform, returning each time to the carriage, and was the last person to leave the train. He has received the Queen's commendation for bravery and was told by the coroner that his behaviour had been "cool, calm, collected and courageous … I cannot believe that the brave Mr Biddle would have survived his horrific injuries but for your intervention."

Earlier, the inquests heard moving statements from family members of the six people who were killed by Khan, the ringleader of the four suicide bombers.

Katie Brewster, daughter of Michael Brewster, 53, said her "sensitive" father had wept after the 9/11 atrocities and urged his daughter to "hope nothing like that ever happens to us".

"His main achievement was as a husband, father, son, brother and friend," his daughter said. "He was a big kid and has been described by those who knew him as bubbly, outgoing, popular and gregarious. There was never a dull moment with him."

Graham Foulkes, father of 22-year-old David Foulkes, fought back tears as he spoke of his pride in a young man who was "missed beyond words by all who knew him".

"I couldn't say what the future would have been for David. Who could? But I do know that he would have made us proud and happy parents."

The inquests continue.