The Sussex Border Path is a long-distance footpath around the borders of Sussex, a historic county and former medieval kingdom in southern England. The main path is 240 km long and stays close to Sussex’s borders with Hampshire, Surrey and Kent, connecting Thorney Island to Rye. There is also an additional 53 km spur known as the Mid Sussex Link, which links East Grinstead with Fishersgate and Mile Oak on the western boundary of the city of Brighton and Hove.
https://en.wikipedia.org/wiki/Sussex_Border_Path

https://www.openstreetmap.org/relation/1002129#map=9/50.877/-0.051

I discovered this when spotted the Mid Sussex Link on my exploration of the countryside around Brighton and Hove area. Recently I completed my first leg of the Mid Sussex Link and intend to do some exploring along the Sussex Border Path next year. I spent a weekend in East Grinstead this year and there was some stunning landscape that I’ll happily explore.