Originally Posted by
DaveReidUK
I don't think there was ever a northside ramp west of the tunnel, just a continuation of the parallel taxiway that eventually rejoined the northern runway at the 09L (10L) threshold, just past the threshold of the relocated 15R (originally 16R), opposite what is now exit A11:
Look above the two 15R thresholds; there's a site outside the taxiway with connnection to the taxiway. This was originally an air defence radar unit (nothing to do with airport ops) for Ground Controlled Interception (GCI) ie vectoring fighters onto attacking aircraft.
It was operational from WW2 until the mid '50s when its function was transferred to a new unit at Chenies, just south of Bovingdon airfield and the site was then occupied by Southern Air Traffic Control Centre controlling civil aircraft in controlled airspace around the south of England who moved in from Uxbridge.
This was later joined by Heathrow Radar, an RAF ATCRU ie not air defence and the two operated from this site until 1971 when they moved to RAF West Drayton, Southern ATCC being re-named London ATCC in the late '60s and Heathrow Radar becoming London Military Radar..