Just how vigilant can the police be as the days turn to weeks and the weeks turn to months? Embassies must get quite a few visitors, and they can't search everyone as they're coming and going. Suppose that Assange grows a beard and dyes his hair, and then one day in a couple of months' time one of the visitors to the embassy is a bearded man with the same hair colour and general build and face shape. They swap clothes, and Assange leaves. He's then put on a train to Bristol and a boat to an Ecuadorean registered ship in international waters. Then the other guy leaves the embassy.