Cape Cornwall

For a long time this was believed to be the most westerly point in the UK, until the Ordnance Survey showed that Lands End, 4 miles to the south, was also slightly further west. Probably a good thing as Cape Cornwall is nice to visit but Lands End ... not so much. Given to the nation thanks to baked beans! The chimney was from a not-very-successful tin mine, and was intentionally left as an aid to navigation.

I'm not sure if it is visible on the uploaded version, but in the original you can fairly clearly see the Isles of Scilly on the horizon over the chimney: 28 miles away.