From BBC News:
"Passengers will remain subject to the new security processes we therefore ask anybody intending to fly tomorrow and over the weekend should arrive at the airport prepared.
"This means arriving with no hand luggage, bringing those items allowed into the cabin in a clear plastic bag and being prepared for delays."
So, in hand luggage:
"All cabin baggage must be processed as hold baggage and carried in the hold of passenger aircraft departing UK airports.
Passengers may take through the airport security search point, in a single (ideally transparent) plastic carrier bag, only the following items. Nothing may be carried in pockets:
- Pocket-size wallets and pocket-size purses plus contents (for example money, credit cards, identity cards etc (not handbags)
- Travel documents essential for the journey (for example passports and travel tickets)
- Prescription medicines and medical items sufficient and essential for the flight (eg, diabetic kit), except in liquid form unless verified as authentic
- Spectacles and sunglasses, without cases
- Contact lens holders, without bottles of solution
- For those travelling with an infant: baby food, milk (the contents of each bottle must be tasted by the accompanying passenger) and sanitary items sufficient and essential for the flight (nappies, wipes, creams and nappy disposal bags)
- Female sanitary items sufficient and essential for the flight, if unboxed (eg tampons, pads, towels and wipes)
- Tissues (unboxed) and/or handkerchiefs
- Keys (but no electrical key fobs). All passengers must be hand searched, and their footwear and all the items they are carrying must be X-ray screened.
- Pushchairs and walking aids must be X-ray screened, and only airport-provided wheelchairs may pass through the screening point."