New CCTV of the July 7 bombers calmly planning and embarking on their suicide mission was played at the inquests into their victims' deaths today.
The grainy and jerky footage showed the four men buying supplies, carrying out a reconnaissance trip to London and then setting out on their final journey.
A police expert said they appeared not to care about being caught on video and acted "completely natural" as they finished their preparations for the deadly attacks.
Scotland Yard launched a massive trawl of thousands of hours of CCTV images after the 2005 bombings on London's transport network, which left 52 innocent people dead and more than 700 injured.
Four days later a police officer with a military background spotted the bombers on film, wearing large rucksacks and walking two-by-two through King's Cross station in central London.
Detectives narrowed down their search and found video evidence that the men had together boarded a train from Luton bound for the capital.
Clips played to the inquests showed Jermaine Lindsay, 19, arriving at Luton railway station just after 5am and fellow bombers Mohammed Sidique Khan, 30, Shehzad Tanweer, 22, Hasib Hussain, 18, parking alongside him two hours later.
The blurry black-and-white images, captured from a distance in a steady drizzle, then depict the four men putting on the heavy rucksacks packed with homemade explosives.
Appearing overdressed compared to other travellers in heavy coats, they walk into the station in pairs and board the 7.25am service to King's Cross Thameslink.
Arriving in the capital, they transfer to the Underground, following close behind a little girl in a pink coat hand-in-hand with her mother.
The final image of the four bombers together at King's Cross before they split up to travel to their targets was also the first to be recovered by police, the hearing was told.
Detective Inspector Ewan Kindness, of the Metropolitan Police, co-ordinated the team of more than 100 officers responsible for finding and examining CCTV relating to the 7/7 attacks.
King's Cross quickly became a key location because all three Tube trains passed through it and the number 30 bus stopped nearby, the inquests heard.
DI Kindness said the bombers were first spotted on July 11 by officers examining a temporary system of 76 cameras at the station.
"The officer engaged in CCTV recovery was ex-military. He saw four individuals walking through," he said.
"They were walking two-by-two and he thought it was significant. They were carrying large rucksacks. He brought it to my attention and I concurred with him that it was a priority for us."
DI Kindness said police were frustrated by the way that some organisations routinely wiped footage after a short time, including London Underground, which only held video for seven days.
Witnesses described the stages of the bombers' journeys to London on the morning of July 7.
Grandmother Sylvia Waugh said one of the men glared at her as she watched them setting off from their bomb factory in Alexandra Grove, Leeds, at just after 4am.
She told how she was woken by voices outside her bedroom window and pulled aside her net curtains to see them loading what she believed were rucksacks full of drugs into a car.
Khan, Tanweer and Hussain then drove out of Leeds and onto the M1 in a rented Nissan Micra, the inquests heard.
At around 5am Tanweer stopped at Woodall services, where he filled up the car and bought three Ginsters cheese and onion slices, a packet of Walker's Sensations crisps and two lemon-flavoured water drinks.
Commuter Susan Clarke said she was not taken seriously when she tried to raise the alarm after seeing the four bombers in Luton station car park.
Following the bombings she tried to pass her concerns on to a parking attendant but he treated her as a "fussy old woman", the inquest heard.
Barrister Ben Leech, who travelled to London in the same carriage as the bombers, said the four men were "sharing a joke, laughing, smiling and generally relaxed".
But another passenger, former University College Hospital researcher Carl Sylvester, said the terrorists did not make eye contact or speak to each other on the train.
Paul Gransby, a project designer for a construction company, told how an "aggressive" Hussain crashed straight into him at King's Cross station just before launching his attack.
CCTV of the bombers on a reconnaissance mission to London a week before the atrocities and buying their final supplies was also played to the inquests.
On June 28, Khan, Tanweer and Lindsay caught a train from Luton to King's Cross and travelled around the Underground.
They stopped at Embankment, South Kensington and Baker Street stations before returning to Luton less than four hours later.
DI Kindness said the trio appeared to show no appreciation that they were being recorded by scores of security cameras.
"There was no overt activity to avoid CCTV footage. They acted completely natural, from my perspective," he said.
Khan, Tanweer and Hussain were caught on camera buying pliers and lightbulbs - apparently for use in their bomb detonators - at a B&Q store in Beeston Road, Leeds, on July 4.
The next day Khan was filmed visiting Dewsbury Hospital in West Yorkshire with his heavily pregnant partner, Hasina Patel.
And the day before the attacks, Khan and Tanweer were captured on CCTV at an Asda supermarket in Pudsey, near Leeds, buying ice packs to keep their homemade explosives cool.
Hugo Keith QC, counsel to the inquests, addressed conspiracy theories claiming CCTV of the four bombers travelling to London was doctored.
Referring to footage taken at Luton station, he said: "There has been a considerable amount of comment on the internet and elsewhere about why this image appears to show a piece of railing passing in front of Khan's left hand side."
DI Kindness replied: "At that exact point Khan has his elbow bent at 90 degrees and you see the railing under his arm.
"There has been no skullduggery with that image at all. It is exactly how it was taken at the time."
The hearing at the Royal Courts of Justice in London was adjourned until tomorrow.Reuse content