Since we didn't have a lot of time to explore London, we decided to spend money on the open-top hop-on-hop-off bus tour. Valid for 24 hours, the 20 GBP ticket not only provided a guided tour of the city, it also included in its package up to 4 city walks, and a boat ride along the Thames.
We first decided to get off the bus at Westminster Abbey (described in a different review). After the Abbey, we hopped back on the bus, and hopped off again when at the meeting point for the Beatles Walk. The walk was really more of Rock and Roll Walk, because our very-knowledgeable tour guide did not only bring us to spots where important milestones in the history of the Beatles took place; he also brought us to places important for other rock stars as well: the place where Eric Clapton first performed publicly at the age of 16; the place where Jimi Hendrix performed "Sgt. Peppers' Lonely Hearts Club Band" with Paul in the audience, just two days after the record had been released; a studio where a number of famous rock stars had recorded some of the best rock songs ever (including some Beatles songs and Queen's "Bohemian Rhapsody"), etcetera... The walk took about 2 hours, and we enjoyed speaking with our guide who was clearly a bona fide lover of rock and roll.
We completed the rest of our tour the following day. We started at the Thames, where we took a boat tour along the river, guided by a very funny guide. After that, we rushed back onto the bus and finished the remainder of the loop that we had missed the previous day. The guide gave thoughtful and sobering accounts of the Plague and the Great Fire of London as we entered the City of London.
On the whole, an open-top bus tour is an easy way to see the whole city if you don't have a lot of time. The quality of tour guides on the buses varies (our first guide was very good; the second seemed to be a bit bored by her job), however, so if you catch a bus with a good tour guide, you may want to stay on to listen to his entire commentary.
Big Bus Company tickets can be bought on the buses, by telephone (+ 44 20 7233 9533), at www.bigbus.co.uk or from the Big Bus Information Centre at 48 Buckingham Palace Road.