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.

Six buildings in central London are royal palaces – but only three of these (Buckingham Palace, Kensington Palace, and Saint James’s Palace ) are still used as homes by members of the royal family. In addition, Clarence House is a royal home but not a royal palace. Three older palaces (Placentia Palace, Richmond Palace, and Nonsuch Palace) on the outskirts of London have now vanished except for memorial plaques while Windsor Castle, Hampton Court, and Kew Palace are intact and open to visitors. Windsor is the royal family’s oldest home, and where Saint George’s Chapel is the final resting place of many monarchs, including the late Queen Elizabeth I.