I dont normally bother to take photos in flight, but had my camera out as this was on board the AF A380 CDG - LHR.
We were in a holding pattern to the east of London and I recognized STN and we flew over the Thames estuary right over the Dartford Crossing and then this airfield shortly afterwards, and we flew in a circle three times.
I assumed it was Biggin Hill, but a quick check of google maps shows it is not. Not Redhill either, nor Headcorn as I went there.
I checked out Southend, Stapleford, Duxford, North Weald & Elstree in case I was going mad and was back over the river again, which we must have done to have gone over the Dartford bridge 3 times.
I know someone on here will be able to identify it!
Bingo - thanks blooBirdie. Thought I knew all the airfields in London, but never heard of this one. It did occur to me after posting there was a distinct lack of aircraft on the ground and markings on the runway and other infrastructure.