I feel Black Combe deserves a mention in this thread.
Growing up in South Cumbria I remember hearing that from the summit of Black Combe you can see a village called "Talk on the hill" near Newcastle under Lyme in Staffordshire (c 90 miles). I don't know who saw this or how it was checked.
Looking online I found;
hearsay...Colonel Mudge, of the Ordnance Survey, thought the view from the summit the most extensive in Britain. You can see, sometimes, fourteen counties, the Isle of Man, and Ireland
The view to the south is said to be the greatest distance in England, to Jack Hill, Staffordshire.
Apparently Mudge saw Ireland "more than once" but "never when the sun was above the horizon"
I remember on many occasions seeing both the mountains of North Wales (c 70+ miles) and Southern Scotland (c 50+ miles) from the beach at Silecroft. The Isle on Man looks almost swimable but is 42 miles away.
Snowdon from Black Combe is c88 miles.
Wordsworth was quoted as saying that "the amplest range of unobstructed prospect may be seen that British ground commands".