Longest line of sight (UK)

[Altrincham]

These are great replies.

I saw the same sight again of Birmingham’s skyline a couple of nights ago, this time further along the Ashbourne to Leek road, and then the Weaver Hills blocked out the view. It sounds like Harboro Rocks could be the furthest north that the skyline of Birmingham is visible from.

 

[Taunton]

Not sure but one dynamic panorama-generating site revealed that you could see France and I think Alderney from the top of the Isle of Wight's Chillerton Down transmitter.

I missed this one earlier, but in the 1960s when Channel Television, a small ITV region, started up, and before satellites were readily available, they had a microwave link from a Westward Television transmitter on top of Haldon Hill behind Teignmouth, Devon, to a receiver on Alderney (and then a link onwards to Jersey). Microwaves travel in dead straight lines so the two aerials must have been line-of-sight with one another. I can't see any record of how high they were.