Designed to link the main tourist traps of Covent Garden, the London Eye, the Tate Modern, the London Dungeon and Tower Bridge, the RV1 also serves a useful commuter function to and from Waterloo and London Bridge stations, and at a leisurely pace aided by a very generous timetable.

The vehicles themselves were a pleasant surprise. After suffering some of the heaps Mercedes-Benz have put out as buses (the 811D minibus and the O.405 single-decker), they've really got it right with the ultra-modern Citaro. Eleven of these all-German citybuses were delivered to First London to run the RV1 out of Hackney garage, and feature 'next stop' LCD screens inside the saloon, an innovative rolling suspension that drops the front to the kerb at each stop automatically and then retracts it afterwards, and discreet air-conditioning. I particularly like the forward-facing seat over the nearside front wheelarch, and make it my home every time I take the RV1. There's even room to stash your bags to the left of you, and the seat is high-backed!

On 1st May EC 2001 (LT02 NTV) stops off at Upper Ground, underneath the southern end of Waterloo Bridge. At about 5 pm on a spring afternoon, this is a particularly good spot to photograph these vehicles - if there are passengers waiting to hail them, that is.