Just Curious

Why would suicide bombers use timers?

Could it be that the bombers did not know what they were carrying or, if they did, believed they were transporting them somewhere else?

"The Observer has been told that police have virtually ruled out the terrorists having been on a suicide mission as the injuries to commuters on the tube trains indicate that the bombs were placed on the floor, probably near the doors. They have established that all the tube blasts occurred within 50 seconds of each other, suggesting the bombs were detonated by timers, not people. The details suggest a more professional operation than was thought at first."

None of the bombers seems to have been particularly radical in his beliefs according to the various profiles, although of course we await more details on what they got up to abroad.

If they were carrying timers, their deaths may be explained simply by the fact that they miscalculated. But even that leaves a serious question: Who set the timers?