The Wales Coast Path[0] links up with it, so (aside from the small gap in Cumbria), you can walk all the way round if you start and end at the Scottish border.

There’s also the Hadrian’s Wall Path[1] that allows you to link back into a loop new the Scottish border, though it misses out a section of the English coast in the North East.

[0] https://en.wikipedia.org/wiki/Wales_Coast_Path [1] https://en.wikipedia.org/wiki/Hadrian%27s_Wall_Path