From this months Pilot magazine
Safety or Security? A B737 crew forgot to set QNH when approaching Gatwick- they were distracted by new security procedures with an intercom call from the cabin- fortunately the weather was CAVOK. And a B737 Co-Pilot who left his seat to unlock the flight deck door, so food trays could be removed, left ATC unmonitored during two flight-level clearances. The locked door was part of revised security.