The terrorists responsible for the Tube and bus attacks in London have been revealed as home-grown suicide bombers. The four young British men, all thought to be of Pakistani origin, are believed to have blown themselves up with rucksack bombs on Thursday, killing at least 52 people. Three of the bodies of the terrorists responsible for what was the first suicide bombing in western Europe have been identified, while a fourth is thought to be among the remains in the wreckage on the Piccadilly line between King's Cross and Russell Square. Police raids at six homes in north Yorkshire yesterday also led to one arrest. But senior security sources warned last night that they suspected al-Qa'ida planners ­ bomb-makers and organisers ­ were still at large and further suicide bombings were likely. The four men, including one teenager, all from Leeds and Dewsbury in West Yorkshire, were not considered Islamic extremists and were not thought to have significant links with terrorism. The realisation that British nationals are prepared to make suicide attacks has transformed the way the country will have to view security.