For the survivors of London’s July 7 bombings, living comes at a price. For some there are moments of unalloyed joy in having come through; for others there are nightmares, flashbacks and panic attacks — dark memories that are not fading with the passage of time.

It is nearly three months now since John Simmons boarded a train on Thursday morning at King’s Cross station to go to work. Normally he would have taken an earlier Tube to avoid the rush hour, but on this occasion he had slept in. It was just before nine when he stepped into the second carriage of the Piccadilly line train. It was crowded and he rammed himself against the door. Seconds after the train pulled out of the station, the bomb exploded.

“I thought the train had derailed,” he remembers. “There was dust and soot everywhere and it was black. People were using their mobile phones as lights. I could see silhouettes of people who were not moving. Bleeding faces were dripping black, not red, because of the soot.”

He remembers there being screaming and then calm, with people passing T-shirts around to bind gaping wounds. Next to Simmons a young man was bleeding profusely from the head and chest. As the emergency services arrived in the next few minutes, he helped him to safety. “He kept saying he was going to die. I would like to find him now, but all I know about him is that he had a Scottish accent. I want to know if he pulled through.”

Simmons considers himself fortunate to have survived the terror in which 52 died and hundreds were severely injured. Glass penetrated his ear, he suffered smoke inhalation, perforated eardrums and a head wound.

Others, such as Martine Wright, a 32-year-old marketing manager who lost both legs above the knee when she was pinned in the wreckage of the blast at Aldgate, suffered grievously.

“I’d been twisted round 90 degrees and I looked at my legs, there was all this metal wrapped over them,” she said last week. “But I could see my legs in the metal, my jeans were all ripped and there was blood everywhere.”

Danny Biddle, 26, lost both legs and an eye and spent four weeks in a coma after the explosion at Edgware Road. The train doors had crushed his legs.

The litany of suffering continues. Louise Barry, 29, a marketing director, was at the back of the No 30 bus in Tavistock Square. Despite a broken neck she was able to crawl out of the debris. She had to endure a titanium cage screwed into her skull as part of her treatment but now wears a neck brace.

“My neck is still broken but doctors tell me it has started to fuse at the top. I cannot move my neck up, down or to the side. I cannot wash my hair,” she said.

Gill Hicks, 37, who lost both legs at King’s Cross, was the last person to be brought out alive from the buckled carriage. “There was one very clear point when I looked round and said: I am not going to die down here,” she said last week. Her heart stopped twice on the way to hospital and she had lost 75% of her blood.

Garri Holness, 36, travelling just a few yards away from Hicks, lost his lower right leg. Rehabilitation at the Douglas Bader Centre at Queen Mary’s hospital, Roehampton, where he and Wright are both patients, will be a slow and painstaking affair: “After the blast I put my hand down to the floor and felt bone and flesh and goo. I put my hand down on the other side of me and felt the same.” Holness, who has just had his artificial leg fitted at the clinic, is hoping to make a full recovery: “I just want to get back to the gym.”

Whatever the scale of injury, whatever the loss of limb, the road to recovery is an uncertain one for all concerned. For those who boarded the fated bus and trains that morning, their lives were changed in an instant. How do we calculate their loss? How can we measure each person’s pain? There is no sliding scale of suffering. A man who loses a leg may make a better recovery and return to work sooner than someone whose hearing is permanently impaired. Suffering is not a competition.