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.

On the Aldermanbury side of Guildhall, you will find the London Centre, the base for New London Architecture and home to its magnificent London models. These 3D scale models of the capital and its buildings are a great resource if people want to see the architecture of London or the historical development of the city—or simply want to trace routes across the metropolis. Their sheer size is jaw-dropping.