This company operates in several cities worldwide, but in London, it shines via special access and innovative offerings that make for an intelligent replacement for tour buses. These include the exploration of Parliament, which go into spaces most groups can’t, and the walk of famous Highgate Cemetery, which gets you into the locked Western portion. It also sells passes that let you jump in on any of its scheduled tours and “London in a Day,” a guided tour that takes care of admission to Westminster Abbey and the Tower of London, a Thames boat ride linking them, and the Changing the Guard.