London bombers may have been tricked 

British police are considering the possibility that the four key suspects in last week's London attacks may have been tricked into setting off their bombs, a British newspaper has reported.
  
"We do not have hard evidence that the men were suicide bombers," a Scotland Yard spokesman told The Sunday Telegraph. "It is possible that they did not intend to die."
  
According to the paper, one police hypothesis is that the bombers were tricked by a "master" who told them they would have time to escape - when in fact the devices were set to go off immediately.
  
"The bombers' masters might have thought that they couldn't risk the four men being caught and spilling everything to British interrogators," an unnamed security official told the Telegraph.
  
Lending weight to the theory is the fact that all four men had paid up their parking tickets before boarding a train at Luton for King's Cross, and that they all bought return tickets to the capital.
  
Moreover, the paper said, the men were carrying their explosives inside rucksacks, as opposed to strapped to their bodies as is common practice among suicide bombers.
  
None were reported to have cried "Allah Akbar" (God is Greatest) before setting off their charge - something which most Middle Eastern suicide bombers do.
  
"It is possible they were duped into believing there would be a delay, but what we know is that they carried bombs onto Tubes and a bus and set them off, killing themselves and innocent people," one senior officer told the paper.
  
"But we are keeping an open mind until we have firm evidence one way or another," said the officer.
  
Police have based their theory that the attacks were suicide bombings largely around the fact that all four suspects died in the attacks.
  
The fact that one of the bombers was decapitated - a common outcome for suicide bombers - is also seen as supporting the theory, as well as the fact that investigators discovered no timer devices.
  
Sir Ian Blair, the head of London's Metropolitan Police, said on Thursday that the attacks had been suicide bombings.
  
"They went onto those Tubes or bus to kill, and presumably accepted they would be killed," he said, adding: "You don't need to be a suicide bomber in a liberal democracy. They've chosen to be."