I drove a Routemaster. What else is there to say. If you're of the age when you can remember the classic London bus, you will love driving one. We did all three buses, the Routemaster, the bendy bus, and the modern bus and, of the three, the Routemaster was far and away the easiest to drive, with the bendy bus the hardest. But don't take my word - try it.
It's not a particularly cheap experience. but it's a one off. Don't miss it.