The crew entry door is used for last minute entry, especially if the engines are running. Kept open, with ladder installed, until just prior to taxi.
The crew entry door is also a parachute exit, but of course the RAF crews will not be able to use it as such because they will not be issued parachutes (is this a WW1 commemorative thing?).
If there were to be an accident where the crew are lost, but if parachutes had been available could have survived, how many senior officers will be prosecuted?
NB provision of parachutes does not guarantee survival but its better than riding the wreckage down and dying in the normal manner.