Terrain Creep?

[Tinkickef]

Had a flight in my spit this afternoon.  Instead of my customary crossing the channel, I thought I would have a sightseeing mission round the coast.

 

Came to the Thames Estuary and flew up it, first time I have been out this way.  On the way to London I noticed two colourful "squares" of terrain, north of the Thames in the middle of the "black" terrain. 

Curious I flew over to them and found two fully detailed, yet still a work in progress patches of land, maybe two miles on a side and five miles apart.  Roads had been put in around them, crossing the black terrain.  The Eastward one hade a chain home station on it, thought Stanmore; yet it looked too far east to be there.  Maps do not seem to show a radar station in that area.

As far as I could tell having no landmarks, I would guess the patches are  located somewhere around the Brentwood / Basildon / Wicklow areas.

 

Following the edge of the "black map" I noticed other terrain creeping.  Lines of trees crossing the black area denoting water courses or rail tracks and roads going nowhere.

 

Last time I visited London, I am sure the detailed terrain ended in a more or less straight line.

 

Are these detailed areas vestiges of an abandoned plan to originally make a bigger map and have always been there, or has someone been quietly beavering away, adding detailed terrain in the background?

Edited March 5, 2022 by Tinkickef