Cockpit Strictly Crew Only
I've heard from someone that the CAA/DfT are implementing a rule that says nobody except crew can now go into the cockpit at all, not even on the ground for flight deck visits after/before a flight.
Apparently easyJet and Aer Lingus have already implemented this.
Seems a bit OTT if you ask me, bit hard for a terrorist to request a pushback and start an aircraft