While rushing from the tube to that pressing appointment in The Ritz's tea room, you may well have missed the Trumpton-style clock that sits above the main doors of Fortnum & Mason's department store in Piccadilly. Mark Mason shows us what happens on the hour and explains why.
Mark is the author of Walk The Lines and website The Importance of Being Trivial.
For more horological trivia take a look at our list of London's most unusual clocks.
