Introduced in 1833, the Timeball was designed to provide ships with a precise timecheck - vital in setting their chronometers for accurate navigation. The system relied on the raising and lowering of a large "ball" on a mast at the top of the Tower at 1pm every day. At 12.53pm, the ball was raised half-way to warn ships to be ready, at 12.57pm it was raised to the top and at 1pm exactly it dropped in response to an electric pulse sent over a landline from Greenwich.

Radio time signals made the Timeball obsolete in 1927 and the building was closed. It was little used until the 1960's, when it served as a council office. It opened in its present role as a museum in 1985.