The Tide Bell at Trinity Buoy Wharf.

Trinity Buoy Wharf, Greenwich, London, near to the Meridian Line. One of this bell’s potential meanings is as a time-piece or time-marker, both in the way the bell is rung by the movement of the sea at high tide daily, and as a long time marker of sea levels and present shoreline. This site is where lighthouse keepers were trained and navigation buoys were made. The bell was installed on Sept 19, 2010.

http://www.marcusvergette.co.uk/trinity.htm