Alan – pretty sure Castle Camps had at least two maybe three concrete runways, and although not much is left today there are still quite big sections of peri-track remaining. A recent google view can be seen here
A couple of pics taken from Grange Road looking NW towards Duxford airfield. The south side of the airfield itself contained a lot of concrete hardstandings and fighter pens, now sadly most are gone.
The original photo on the left is Mark12’s photo i think, taken at the time of the filming of the Battle of Bitain.
It would be great if photos on this thread could be an inspiration to others everywhere to get outside and try and match up some old photos to whats left today.