Like its competition, it offers three circuitous routes, although two of them (Red and Blue) cover much of the same ground and narration is frequently prerecorded (it’s live on Red, recorded on Blue) with out-of-date information. It doesn’t matter at which of the 50-odd stops you get on, but since drivers often change at Green Park on Piccadilly, you can avoid that wait by starting there. Most people get on at Marble Arch, Regent Street south of Piccadilly Circus, Charing Cross Road north of Trafalgar Square, or under the South Bank Lion at Westminster Bridge. Prices can be a few pounds higher if you don’t book ahead.