I stumbled across Wisley Airfield [0] one day - very strange, doing a long bike ride across London, I plotted a route that avoided main roads and suddenly found myself in the middle of a mile-long runway. Right next to the A3 and RHS Gardens at Wisley, not a lot of people know about it. There's a public bridleway across it, no problem for anyone who wants to explore; last time I went past, there was armco across the runway which I think might be to stop illicit drag races.
Here in Sweden we have a lot of (military) airstrips that are incorporated into the public road network.
It's always strange when you bike on a rural road and it broadens to a four lane motorway straight ahead for a kilometer, and then it narrows again and meanders on.
When they were building the M25 motorway around London (about 120 miles for the loop) there were large sections that were built and not yet open to the public - much fun was had on fast motorbikes late at night! Though once the whole thing was open, it all got out of hand [0]. Having said that, back then you weren't risking serious jail term for high 3 figure speeds (on top of the risk of losing your licence, and potentially your life).
In the grass north of the runway, you can see a pattern of scars, all the same length, mostly orthogonal, and a few diagonal. These are almost surely archaeological trial trenches:
Often these are dug to evaluate land before it is built on, in case there is important ancient stuff that will be disrupted or buried. That hints that the airfield may be about to be redeveloped.
You are very likely right; every few years I look it up to see what's happened to such a large chunk of undeveloped land right next to one of the main A roads into London. Here's the current first hit on Google (for me):-
[0] https://www.google.co.uk/maps/search/wisley+airfield/@51.303...