I assume there is an indication on the flight deck when this door is opened. It's just that a few weeks ago at LHR I heard the crew of such an aircraft call for start clearance. The controller obviously had a quick look out the window and replied "confirm fully ready for start?". "Affirm", came the reply. The controller then said, "It's just that it looks like your rear door is still open. Anyway, start approved and make sure it's closed before you go..."