At 8.51am a year ago on Friday a bomb exploded on a London Underground train near Aldgate. In less than a minute, a second device detonated at Edgware Road. Fifty seconds later a third bomb deep in a Tube tunnel near Russell Square blew off Gill Hicks's legs.
"I was falling in black, liquid tar and my immediate sensation was I was having a heart attack and that I was dying on the Tube. The whole environment was changed. You've gone from a bright sunny world ... suddenly the bowels of the Earth have opened up.
"It was black. Can't breathe, people screaming, what do I do? And I called for someone to pick me up: I remember putting my arms up and saying 'I can't feel my legs.'"
Then the emergency light came on and the 37-year-old saw terrorist bomber Lindsey Germaine's handiwork.
"My legs did look like a picture of an anatomy drawing of what the inside of your leg looks like and my feet were both surgically severed but still connected to what remained of the lower part of my legs," recalled Ms Hicks in a BBC interview last year.
On 7 July 2005, Germaine, Mohammed Siddique Khan, Shehzad Tanweer and Hasib Hussain killed themselves and 52 others in the worst ever terrorist assault on London.
While rightly proud of their refusal to be intimidated in the wake of the bombings, Londoners recall the tang of fear on buses and Tube trains in the weeks after the attacks, particularly after a second attempted bombing a fortnight later. Trains seemed to be stuck for longer in tunnels more airless than ever. Young, bearded Asian men were advised not to carry rucksacks on public transport.
That unpleasant frisson will be felt again by many of the millions of commuters travelling on Friday. Mental health experts warn that many of the 7/7 survivors will be experiencing "anniversary reaction", oftenas severe as the feelings in the immediate aftermath of a major disaster. And it will not only be those injured in the attacks who will suffer, but also those who appeared to be unharmed.
Professor David Alexander, one of the country's leading experts on trauma, said it is normal for those affected to become increasingly anxious as the anniversary approaches.
"The most likely impact will be that people experience flashbacks from that day in the form of noise, smell or even touch," said Professor Alexander, director of the Aberdeen Centre for Trauma Research at Robert Gordon University in Scotland. "There will be a renewed anxiety of travelling on the Tube. It is a pity, although perfectly understandable, for people to avoid anniversary events, because these can help with the healing process and make them realise that other people feel the same way."
Many of those affected by the bombings are only now seeking counselling; others are too traumatised to attend the anniversary service. Eamon Spelman, who was in the second carriage of the train which was blown up at King's Cross, attended the six- month commemorative service but says he fears the emotional trauma of attending this week's event will be too much for him.
"Something like that takes days to get over and I am not sure I want to go through that again," said the 47-year-old carpet buyer for Harrods. "I can't put it behind me yet, I need the anniversary to pass before I can start to move on. Some people will want to be together on 7 July but I think I will want to be alone - at least for the two-minute silence."
Chrissy Fullbrook, who was also on the Piccadilly line train, was not physically injured but did suffer mental trauma. It is only now that the 42-year-old officer manager has felt able to seek professional help.
"I thought that I was OK and that because I wasn't physically injured I had nothing to worry about," she said. "But I walked away with mental problems that have taken this long to surface. I attended my first counselling session last week."
Intelligence services are understandably anxious that extremists may see this week as an opportunity to launch fresh bombings. MI5briefed MPs on the possibility of an anniversary attack last week. The Intelligence and Security Committee (ISC), the group of MPs and peers hand-picked by Tony Blair to oversee the security and intelligence services, were told that alerts are close to their highest level. Tomorrow police will urge extra vigilance in the coming weeks. But as they do so, many questions raised in the aftermath of the attacks remain unanswered.
According to the official Whitehall-authored narrative, the four bombs, three on trains, the last on a bus, were the work of a self-radicalised cell working alone on a budget of £8,000. The bombs were home-made. There was no evidence of a mastermind nor of a network, other than a loose, social nebula of radical Islamists.
This "clean skin" version, published in May, was given an apparent parliamentary rubber stamp by a report from the ISC released at the same time. The ISC effectively cleared the intelligence and security services of any failure, asserting that none of the four bombers had been identified as a potential terrorist and that the attack had happened without warning.
Reassuring these reports may be, but they are wrong, according to the respected terror analyst Nafeez Mosaddeq Ahmed, a tutor in international relations and politics at the University of Sussex. His new book, The London Bombings: An Independent Inquiry, pulls apart the official narrative of 7/7, pointing out its gaps and contradictions. He concludes that the security and intelligence services, with government connivance, downplayed the sophistication of the operation and the size and nature of its support network. Evidence of al-Qa'ida involvement is suppressed, he says, to deflect awkward questions about how a large terror network flourished unchecked in Britain for 10 years.
If he is right, the next wave of attacks to hit London is far closer and more violent than is commonly supposed.
There are some bewildering gaps in the Whitehall account of 7/7; even the nature of the explosives used in the bombing is unclear. The report says only that "it appears" they were home-made, although there is plenty of evidence that the bombs were powered by at least some commercial or military explosive.
"Forensic science ... tends to produce unambiguous answers within a matter of hours and days," Mr Ahmed says. "The idea that continuous examination over many months has failed to finish the job beggars belief."
Furthermore, the substance that the bombers were said to have mixed from household products - TATP - produces neither flame nor heat upon detonation. But eyewitnesses reported both.
Then there is the curious official reticence over proven links between the bombers' ringleader, Mohammed Siddique Khan, and other terrorists, including senior al-Qa'ida lieutenants abroad. Officially, it is admitted only that Khan was on the "periphery" of another terror plot currently the subject of court proceedings. In fact, Khan had been placed on a watchlist in 2004. MI5 had opened a file on him. Mr Ahmed claims the three other bombers were all also known to MI5.
The official narrative baldly states: "The extent to which others may have been involved in indoctrinating the group, have known what they were planning, or been involved in the planning, is unknown at this stage."
The ISC report goes a little further, admitting that Khan and Tanweer probably received "some form of operational training" in Pakistan in the months before the attacks. But Mr Ahmed is amazed that this ignores the telephone traffic between Khan and, among others, Haroon Rashid Aswat, an al-Qa'ida lieutenant previously based in Pakistan, believed by US investigators to be the mastermind of 7/7.
Mr Ahmed's controversial inference is that MI5 is now trying to cover up a tacit understanding with terror groups that operated until 9/11. They were allowed to operate as long as they did not bomb Britain or UK targets abroad. There was, in effect, a "covenant of security", he says.
Radicals such as Omar Bakri and Abu Hamza, who did so much to foment violent Islamism in Britain, were used by intelligence services in a disastrous miscalculation, he contends.
"In systematically downplaying the undeniable role of al-Qa'ida in the London bombings, the official account is attempting to draw public attention from the fact British authorities have tolerated the activities of an entrenched and burgeoning network of radical Islamists with terrorist connections for more than a decade," says the analyst.
On top of this, the Foreign Affairs Committee's report on the war on terrorism released today warns that Iraq is recruiting and training a new generation of international terrorist.
"The insurgency in Iraq continues to blaze, and the situation in Afghanistan has deteriorated," it says. MPs conclude that al-Qa'ida "continues to pose an extremely serious and brutal threat to the UK".
Patrick Mercer, the Conservative spokesman on homeland security, said: "The case for an independent inquiry at the conclusion of on-going court cases is now totally compelling."
Survivors such as Gill Hicks are just thankful to be alive. She will spend Friday with family and close friends, remembering the heroism of strangers on the day London was ripped apart.
"Every single day I thank everyone who rescued me and kept me alive, and I will do so for the rest of my life. I am absolutely committed to living a good and fulfilled life, a life that will 'make a difference', to show my true appreciation for all that was done to save my life on that day."
THE SURVIVORS: 10 TALES OF COURAGE AND ENDURANCE
The reluctant hero
PAUL DADGE, 29, CANNOCK, IT CONSULTANT, WEST MIDLANDS
What happened: Hailed a hero when pictured supporting Davinia Turrell with a burns mask on her face. The attention affected his mother's health. He received death threats from al-Qa'ida.
He said then: "I saw an awful lot of walking wounded. I didn't have time to think about myself. It's my instinct to get involved."
He says now: "It was uncomfortable being called brave when the victims were quietly struggling to get over their own injuries."
The survivors: 10 tales of courage and endurance
The critically injured
Danny Biddle 27, Building Project Manager, Essex
What happened: Lost both his legs, his left eye and his spleen in the Edgware Road blast, so suffering among the worst injuries of any survivor. His heart stopped for 18 minutes.
He said then: "I didn't want to die in the tunnel. When you see people in pieces it's not something you can wipe from your mind."
He says now: "I can still smell the burning flesh when I talk about it. I can still remember the texture of my skull. I thought I was dying."
Mark Margolis 29, Software Project Manager, Finsbury Park
What happened: Suffered facial injuries in the Piccadilly line blast. Went back to work almost immediately. Now avoids the Piccadilly line. On all other Tube trains always travels in the front carriage.
He said then: "I just heard a bang and all the lights went out. Glass flew, people were screaming. I feared fire. If there was a fire I don't know how we would have got out of there."
He says now: "The anniversary is about the dead and their families."
The post-traumatic stress victim
Kirsty Jones 38, Designer, Stoke Newington
What happened: Was in the last carriage of the Piccadilly line train bombed by Germaine Lindsey and trapped for half an hour. Several months later she suffered a panic attack and was diagnosed with post-traumatic stress disorder.
She said then: "It suddenly hit me that people had been dying in the train I was travelling in."
She says now: "I will probably go to work and complete the journey that I never managed a year ago."
Martine Wright 32, Marketing Manager, Stroud Green
What happened: Martine was the last survivor to be pulled from the Aldgate bomb. She lost both her legs and is now planning to learn to fly and ski.
She said then: "It was a Tube then it wasn't a Tube, just devastation, black devastation and I'm thinking, where has it gone?"
She says now: "I still sometimes think that my legs will come back. But the reality is they've gone. In many ways I've been given a new lease of life."
The anxious survivor
Eamon Spelman 47, Harrods Carpet Buyer, Bounds Green
What happened: Travelling in the second carriage of the Piccadilly line train, his hearing was impaired, and he has now begun to have flashbacks. He fears the anniversary ceremony will be too much for him, but sees it as a stepping stone to moving on.
He said then: "There were a lot of people with head injuries and blood running down their faces."
He says now: "I can't put it behind me yet. I need the anniversary to pass before I can start to move on."
The chronicler of terror
John Tulloch 63, University Lecturer, South Wales
What happened: Was feet away from the Edgware Road blast that killed six of his fellow passengers. He was left with vertigo, perforated eardrums and head and thigh injuries. During his recovery he wrote a book, One Day in July.
He said then: "I didn't hear a sound at all and then had this very uncomfortable feeling."
He says now: "What happened was unexpected and unpleasant. It should not be forgotten."
The woman who wants to move on
Chrissy Fullbrook 42, Office Manager, Wood Green
What happened: Was on the Piccadilly line train four carriages back from the blast. It takes all her strength to get to and from work every day. She will go to King's Cross at 8.50am on Friday.
She said then: "So many things ran through my mind, but the possibility of a bomb didn't even enter my head."
She says now: "It is something I need to do, to move on."
Garri Holness 36, Advertising Executive, Croydon
What happened: Had part of his leg amputated after being caught up in the Piccadilly line explosion. Led a campaign to increase compensation for victims. It was later revealed that he was convicted of rape 20 years ago and sentenced to seven years in prison.
He said then: "If I had a bad day then they have won."
He says now: "I regret what I did. I have a scar that will never leave. It will stay with me, just like 7/7."
Rachel North 35, Arsenal
What happened: Escaped with cuts and bruises when the Piccadilly line bomb exploded seven feet away from her. Began an online diary of her experiences and later founded Kings Cross United.
She said then: "I felt almost bad for having got off so lightly."
She says now: "I hope I will be able to leave the darkness behind and start to plan my wedding and celebrate the life I nearly lost."
Interviews by Lauren Veevers
How much has London changed since the terror attacks on 7/7?
This week is the first anniversary of the 7 July attacks in London in which 52 people, and the four bombers, were killed. But what has been the long-term impact of the bombings? We went to Tavistock Square, scene of the bus attack, and asked people whether London has changed for better or worse since 7/7. Interviews by Kate Nettleton
Mike Minchinton Human Resources Manager
I try to understand religions, minorities and things that are going on more. I've been on the Tube since; I'm not put off by it. You've just got to carry on.
Michael Henderson Environmental Consultant
We've got more sensationalist and a bit pre-occupied by it all, especially when there's a much greater terror - climate change - to be concerned about.
Claire Wright Media Planner
People are more nervous on the Tube, especially when there are more police around. If there's a bag left alone people will ask "whose bag is this?". They never used to do that.
Maddy Duxbury Public Relations Co-ordinator
People are more aware of their surroundings now, but other than that the atmosphere is back to normal.
Angela Brown Cleaner
People seem on their guard more. Whenever you hear a bang or see bags left around, it makes you feel suspicious. I use London transport much less now.
Danny Millum Librarian
It gave government a chance to plough ahead with things like ID cards. It's wrongthe victims have been eulogisedwhen that number are killed in Baghdad daily.
Kirsten Hindes Executive Assistant
I take public transport every day and I've continued to do so since the bombings. I felt fine afterwards, while some of my co-workers were devastated.
Tim Hodgson Plasterer
I was on a train behind two Muslims and I thought, "that's not what I need". But they're not going to blow up a train to Hampshire are they?"
Steven Bukenya IT Consultant
It's better in terms of the Government being more security-aware. But we are too suspicious of people and probably alienating Muslims even more.
Ivor Grant Taxi Driver
London has changed for the worse but not necessarily since the bombings. It's really changed since Ken Livingstone was elected Mayor. People seem more aggressive.
Jamie McClelland PhD Student
Any change hasn't been for the better. Extra security measures don't make me feel safer, although I only occasionally think about the risks.
Bea Sneller PhD Student
There's still tension on the Tube, especially when there's a delay. It's in the background of most minds but it doesn't much affect everyday life that much.