"I have noticed a group of four police officers standing around in a group chatting near the Tube station close to where I work. Maybe this is deliberate, to get the commuters chatting to each other as well? Fortunately, at London Bridge at least, there is a fifth member of the police team, who is presumably in charge. He is always very alert and business-like. He's also healthy, judging by his wet nose and shiny coat."