It emerged last night that, for the first time in Western Europe, suicide bombers have been recruited for attacks. Security forces are coming to terms with the realisation that young Britons are prepared to die for their militant cause.

Three of the men lived in Leeds and the immediate fear is that members of a terrorist cell linked to the city are planning further strikes. The mastermind behind the attacks and the bombmaker are both still thought to be at large.

The man who planted the bomb at Edgware Road was named last night as Mohammed Sidique Khan, 30, the married father of an eight-month-old baby, who is believed to have come from the Leeds area.

Two other terrorists were Hasib Hussain, 19, who bombed the bus in Tavistock Square, of Colenso Mount, Leeds, and Shehzad Tanweer, 22, the Aldgate bomber, who lived at Colwyn Road, Leeds.

Police are still trying to identify the fourth, whose remains are believed to be in the bombed Tube train carriage on the Piccadilly Line. It is thought that he comes from Luton.

Armed police raided six addresses in West Yorkshire yesterday, including the homes of three of the men, who they now know travelled to Luton in a hired car last Wednesday to join the fourth man. They boarded the 7.40 Thameslink train to King’s Cross the next day, each armed with a 10lb rucksack bomb.

Police found a bomb factory in Leeds containing a “viable amount of explosives”. Explosives were also recovered from a car left parked near Luton station. The raids came after the discovery of driving licences and credit cards at the scenes of the explosions, and a telephone call from the mother of Hasib Hussain, who asked police to try to trace her son.

A relative of one of the bombers was arrested and taken to London for questioning. Intelligence agencies say that at least two of the men had recently returned from Pakistan. All four were British, but with origins in Pakistan. MI6, MI5 and British diplomats were in touch with the Pakistani authorities last night to try to track down any connections with terrorists there. Security sources confirmed that none of the bombers was on any MI5 file, although one had links to a person investigated by police.

The four were captured on CCTV cameras at King’s Cross Thameslink station, laughing together and carrying rucksacks, minutes before they set off for their targets at 8.30am on July 7.

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