For many visitors to London, one of the iconic sights of a trip to the capital is a traditional London red double-decker bus. Known as a Routemaster, these buses was designed in the late 1940s and manufactured until 1968 when production stopped, mainly because their open back doors – which were one of the attractions for many Londoners – made them unusable by those in a wheelchair. They were still used on many routes until the early twenty-first century and some can be seen occasionally on routes such as the Routemaster Heritage Route 15 which runs from Blackwell to Trafalgar Square.

Which is the most important clock in the world? Many visitors to London would answer ‘Big Ben,’ even though this is officially the name of the bell behind it rather than the clock itself. However, as a London blue badge guide, I would say that the world’s most important timepiece is the John Harrison H4 which can be seen in the Greenwich Royal Observatory museum near where the Prime Meridian is marked on the ground.