We went through Marble Arch tube, was told to stay away from Hyde Park entrance by more than one person as the security is tighter there, we had a bag full of drinks and crisps and I had my ecig in hand and not a pat down in sight, the guy just looked in the bag, smiled and said you forgot mine (there was three of us and three of everything).
Contrast that to my local McDonalds where later that evening we were refused entry until we removed our woolly hats, but they weren't bothered about what was in the bags...