Video: 7/7 bombers filmed in Leeds as they bought final supplies

They purchased pliers and light bulbs at a B&Q hardware store and made an early-morning visit to an Asda supermarket for bags of ice to keep their homemade bombs cool.

Plot ringleader Mohammed Sidique Khan was also filmed visiting Dewsbury Hospital in West Yorkshire with his heavily pregnant partner, Hasina Patel, two days before the attacks.

CCTV footage of the suicide attackers calmly making their final preparations was played at the inquests into the deaths of the 52 innocent victims of the London bombings on July 7 2005.

Khan, 30, Shehzad Tanweer, 22, and Hasib Hussain, 18, visited the B&Q store in Beeston Road, Leeds, on July 4.

The men are seen arriving in the blue Nissan Micra hire car - rented by Tanweer from July 4 to 8 - which would be used to transport them from Leeds to Luton on the morning of the attacks.

After parking the vehicle, they enter the store at about 1.50pm and Khan goes over to the returns desk with an item in his hand.

The three men then walk up the aisles looking for the products they need before paying for them and leaving.

A B&Q receipt found at Khan's Dewsbury home after the bombings, showed he bought three sets of pliers and two 50-watt bulbs.

The inquests have already heard that an improvised explosives detonator made from a light bulb was discovered at the terrorists' bomb factory in Leeds.

The next day, Khan and Ms Patel were caught on camera arriving at Dewsbury Hospital in the same blue Nissan Micra.

Khan and Tanweer were also filmed shopping at the Asda superstore in Pudsey, Leeds, the day before the bombings.

Counter-terrorism police quickly spotted the bombers on CCTV as they arrived in London because of their suspicious behaviour.

A former soldier working for Scotland Yard's Counter Terrorism Command raised the alarm just four days later when he saw footage of the four men walking through King's Cross in pairs and carrying rucksacks.

The third day of inquests into the 52 people killed in the 2005 suicide bomb atrocities heard police were caught in a race against time as they tried to collect CCTV evidence.

Detective Inspector Ewan Kindness, of the Metropolitan Police, said he was responsible for coordinating a team of more than 100 officers responsible for finding and examining footage.

He told coroner Lady Justice Hallett investigators worked backwards from the four bombs sites to try to trace those responsible.

But he said police were frustrated because some organisations routinely wiped footage after a short time, including London Underground which only held footage for seven days.

And the hard drive on the number 30 bus blown up in Tavistock Square was corrupt and did not record any information from July 7.

Mr Kindness said King's Cross station quickly became a key location because all three Tube trains passed through and the number 30 bus stopped nearby.

He said the bombers were first spotted four days after the attack as police examined a temporary system of 76 cameras at the London station.

Mr Kindness said: "The officer engaged in CCTV recovery was ex-military. He saw four individuals walking through.

"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."

The inquest heard driving licence images of Hasib Hussain and Mohammed Sidique Khan were recovered from bomb sites and compared to CCTV images.

Mr Kindness said: "Although it was grainy, we were convinced at that stage that they were the same individuals."

The investigation moved to the King's Cross Thameslink station and on to the lines from Bedford and Luton where footage was recovered from ticket halls, platforms and car parks.

By July 12, police had found the four bombers arriving at Luton station in two cars, a Nissan Micra and a red Fiat Brava, which was later towed away.

Examination of Jermaine Lindsay's mobile phone revealed he had travelled to Marylebone on June 28 and CCTV showed he was with Khan and Shehzad Tanweer.

A meticulous study of vehicles travelling down the M1 on the morning of July 7 revealed the Nissan Micra, carrying Tanweer, Khan and Hussain, stopped at Woodall services for petrol.

The inquest heard that the CCTV investigation continued for some 18 months after the attacks.

Some of the huge haul of CCTV gathered by police was shown to the coroner to document how the bombers travelled to London, armed themselves and descended into the capital's rail network.

Footage shot in the car park of Luton station showed Lindsay arriving shortly after 5am and the other three men parking alongside two hours later.

The blurry black and white images, captured in steady drizzle at a distance, then showed the four men gathering at the rear of the blue Micra and putting on their heavy rucksack bombs.

Wearing similar dark anoraks, the bombers walked in pairs into the station and boarded the 7.25am service to London King's Cross Thameslink.

Hugo Keith QC, counsel for the inquests, said they appeared "overdressed" in comparison to other travellers in their sports wear and heavy coats.

Images from a passageway at the London station were the first to be recovered but the last to document the foursome together before they split up to travel to their targets.

Earlier, the inquest watched footage from street cameras and businesses outlining how the Nissan Micra was driven by Tanweer out of Leeds and on to the M1 at about 4am.

At Woodall services, at around 5am, the bomber was filmed filling up with petrol and buying crisps and water for himself, front seat passenger Hussain and Khan.

Tanweer struggled to open the petrol cap of the rented vehicle and could then be seen attempting to force the bonnet closed after releasing it by mistake.

Mr Kindness said investigators painstakingly collected up to 40 segments of film detailing how the vehicle travelled down the M1 until it was lost between junctions 15 and 14.

Mr Keith also addressed one conspiracy theory suggesting a still CCTV image of the four men entering Luton station had been doctored.

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.

Mr 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."