4 Wendover
It's as well the page wasn't headed "where are these?", because while Google has no trouble finding it (on The Signal Box website, which I guess is where that picture came from) in real life it would be harder. Its site is now a narrow strip between the railway just north of Wendover station and the A413. There's
a personal reminiscence of working there with the picture, ending with:
Eventually management decided enough was enough and reduced the peak hour service to run every twenty minutes, so the box could be permanently switched out. It was abolished on the 1st of July, 1984.
Recently, a new bypass has been driven through the field that was behind the box. I made a point of driving that way one day to see how the transformed landscape looked. I expected to see no sign of the box, as the bypass is right next to the railway at that point. Astonishingly, the new railway boundary fence suddenly moves nearer the bypass for a few yards, skirting the foundations of the box which for some reason still remain.
Now, like most other railway borders, it's overgrown with trees so you can't see anything.