There was a Romano-British settlement on Cox's Mount, the summit of Gilbert's Pit, between the first and fifth centuries. The area was part of the ancient Hanging Wood. The Pit was part of the estate of the Maryon-Wilson family. From the late eighteenth century to 1889 it was worked for sand, and it was named after one of the managers, Mr E. Gilbert. It was purchased by the London County Council in 1930.
Gilbert's Pit is an important Lower Tertiary site, displaying one of the most complete sequence of sediments in Greater London. The PaleoceneThanet and Woolwich Beds date to around 55 million years ago. Some of the beds yield many fossils of plants, sponges, molluscs, fish and reptiles. The site has been studied for over 120 years and is the subject of a substantial literature.
Much of the site is fenced off. There is access to the part which is open from Charlton Lane and a path from the Gilbert's Pit information board in Maryon Park leads up to Cox's Mount, which has fine views over London.