Traveling as a tourist you don’t want to stick out too much. I visited London when I was stationed in Germany when I was in the US Army. Back then I would have had nothing more than a small pocketknife. If I were there today I would only have a few pocket items, a LeatherMan Charge Ti, and a SureFire C2. I would have nothing for smoke or first aid. Most places in London there are shops only a few steps away. It would be good to carry a bag with water, a dust mask, and a first-aid kit. I don’t think I would take my CamelBack to London. A backpack will now make you look like a homicide bomber. Most Europeans carry a briefcase. They carry their lunch in it but it would be good as a low profile PSK container.