The Independent reports that:

One of the suicide bombers who attacked London on 7 July was filmed arguing with a cashier about being short-changed hours before he blew himself up.

It was odd enough that someone believing that they were on their way to their death would bother to buy a parking ticket at Luton station, but there was at least a possibly believable explantation of this, about not wanting to draw premature attention to the car. It's also totally unclear why explosives were left in the car (if indeed they were), but again, the official story says that perhaps someone else was going to come and pick these up.

But why argue about being short-changed at a petrol station when you know you are about to die?