Unusual building at Filton. ID please?

Peter wrote:

I too looked at that when confirming the Filton Bofors Towers locations. I had a suspicion it was radar related and thought I had seen something similar covered on this forum - but where?

A Second World War radar station or beacon is visible on historical aerial photographs (including clear oblique views on Aerofilm photographs) and was mapped as part of the Severn Vale NMP project. The military installation is visible south of Filton airfield (Monument Number 1395348) as a sunken building or bunker at ST 59633 79449, with a stepped entrance on its south side and another diagonally opposite on its north side. A tower with a high walled octagonal observation platform is centred in the middle. Its exact function is not clear though it had a radar scanner attached by 1980 and stayed in use until 2009, though the observation tower appears to have been partially removed. This continued use as a radar station may suggest its earlier use during the Second World War. Another possibility is this served as a Sector Operations Room for RAF Fighter Command, for which there was one at Filton.

It’s located close to the battle headquarters and is defended by two pillboxes (Monument Number 1591766 and Monument Number 1591764) to the east and north. There are also numerous slit trenches and a possible communication trench and barbed wire entanglements (Monuments Number 1591791) which also add to the defence of the locality. To the south is an army camp (Monument Number 1591792) which may have served as accommodation for this installation and/or the adjacent defences.

Though the tower has been removed and the bunker is disused it is still visible on recent aerial photographs taken in 2013.