Before I retired from Agricultural Contracting, one farmer requested I plough his 40 acre 'Light Field'. About half way through the job, the old Ransom Plough started to dig up big chunks of brickwork, (which I took to the edge of the field.).
When I asked what that was all about, I was informed it was for the air-ministry WW2 Light foundations. Apparently the light was a Navigation aid, which was switched on to help returning aircraft, and was exactly 3nm from the end of the airfield runway.
I looked for any similar structures at the 3 mile distance from the other runways, but could find no trace of anything, after all these years.