Way back in 1788 the beach & much of Eastney was purchased by the Crown for the Defence of the Realm and was used by the Admiralty. This passed, over time, to the War Dept, then to the MoD’s Defence Evaluation Research Agency (DERA). It passed more recently to QinetiQ (the privatised DERA), taking the beach from public ownership into private hands and thus gifting a nice windfall property to QinetiQ’s shareholders. For more on this take a look at the What’s the problem? page.
The concrete blocks along Fraser Beach are also of historical interest – they’re one of the finest examples of anti-tank blocks from WWII and are now listed as a scheduled monument.