Originally Posted by
treadigraph
That's got to be Leavesden - the hangars were at the top of a steep bank above the A41. Eagle Aviation usually had several King Airs on the ramp... when I was 15 I walked from Borehamwood station to Elstree, then Leavesden and ended up at Watford station!
https://maps.app.goo.gl/mXSiE5Nr55gCfHks7
Thanks treadigraph, that definitely looks like it. We were heading from Newcastle to somewhere near Windsor (pre-M25) so it looks like exactly the right area. Thanks also to DHfan for the suggestion. I looked at Denham and it's in the right area but the embankment didn't fit.