The remain of earthworks surrounding the Iron Age Fort are still very prominent on the ground.
Tees Archaeology have produced an excellent leaflet on the subject here.
The Napoleonic Beacon was built in 1808 as part of a chain to warn of attack.
The actual watchtower appears to have been built and little later around 1819/1820 (thanks to Joan for the additional information), that later became a private residence and was inhabited up until the 1950s.
The view from the top is still spectacular