I'll second Danny's comment about the financial side - I can't take through my litre bottle of water, I can't take through an empty litre bottle and fill it from a water fountain airside, but I can buy an overpriced bottle of water from a shop once I'm in the lounge and take it on the flight. Just wait until they stop us taking chocolate bars and other snacks (really useful if flying LoCo) and expect us to buy them at inflated prices once past security.
Anyone know if you can still buy razor blades in Gatwick Duty-Free (or what happens if you actually try to buy them)? I haven't been through there for a while.