Perhaps this has something to do with the recent bomb threat incident at Heathrow & the fact that a cabin crew member was detained. Crew are probably now considered as much of a threat as anyone else (if they weren't already) & perhaps even more so, given their regular access to aircraft.
Is cabin crew want ot bring the a/c down, the just need to put a few oxygen bottles to cook and it's done. So again stupid measures being taken.