In message , at 10:28:25 on Tue, 12 Jul
2005, Ed Lake remarked:
He probably had the bomb in his hand when he boarded, dropping it in a
parcel bin next to the door and leaving again.

The trains don't have any such bins, or indeed anything like them.

In any event, you'd be waiting on the platform (stood behind people who
had been waiting longer than you) as a train arrived, so there'd be
plenty of time if the bomber really was taking individual bombs out of a
larger bag, as you are theorising.
--
Roland Perry