Thanks to a specific terrorist threat all airlines flying out of the UK are not allowing hand baggage. You can still take things like glasses (with out cases), contact lenses (with cleaning solution bottles), babies milk, travel documents, keys (but no alarm fobs) and a few other things on board, but just about everything else will have to be checked into the hold.

They are also carrying out extra searches, at the gate, on all passengers leaving the UK.

http://www.britishairways.com/travel/flightops/public/en_gb