Often referred to as the 'docker's clock', it was built as an aid to ships in the port, as it allowed them to set the correct time as they sailed out into the Irish Sea, while its bell warned of meteorological changes such as high tide and fog. Designed by Jesse Hartley it was constructed between 1847 and 1848, to commemorate the opening of Salisbury Dock. Its design was based upon an earlier drawing by Philip Hardwick in 1846. Upon completion is also served as a flat for the Pier Master. It is a Grade II listed Gothic Revival clock tower positioned between the two river entrance gates to the Salisbury Dock.