Route: Pennine Way (UK)

https://www.nationaltrail.co.uk/pennine-way

"Steeped in history, this National Trail chases along the mountain tops along the rugged backbone of England and offers 268 miles of the finest upland walking in England. A once in a lifetime experience."

The Montane Spine Race covers the entire Pennine Way in winter. The overall course record was set in January 2019 by fell running phenom & nursing mother Jasmine Paris in 83h12m23s:  https://www.bbc.com/news/uk-scotland-edinburgh-east-fife-46906365