For the benefit of those asking what is currently happening at London airports, a domestic flight experience.
Flew with BA to Aberdeen from Terminal 1. Everything very quiet at 5 am. Arrived 1 1/2 hours in advance. Formalities took 20 minutes. Allowed one briefcase sized hand item each through security, plus anything you could buy airside, but no toiletries or liquids. Slightly larger baggage did not seem to be a problem but one girl with a huge rucksack was asked to go back and check it in (how did she get that far?)
Coming back even quicker and people seemed to be allowed larger hand baggage generally in that direction.
On balance, apart from the liquids and toiletries, everything was quite normal.