Now, if only there was a project to deliver freely licensed maps of the world... Let's call it, idk, OpenStreetMap? Sounds cool :^)
Also, I think Ordnance Survey's record of the use of these footpaths has significant weight in keeping them legally protected.
So Ordnance Survey is the best tool here.
This is mine https://explorer.geowessex.com/?layers=48&basemap=26
Definitive maps https://www.ramblers.org.uk/advice/paths-in-england-and-wale...
You're showing me the result - I'm telling you how that gets achieved in practice.
You can read more about it here from a relevant group https://www.ramblers.org.uk/-/media/Resources/Volunteer%20re...
England in particular has a long and complex history of land being gifted by royalty and clergy to sycophants leading to the rest of us being screwed over for literally a thousand years!
Green and pleasant land indeed!
That said, England does have a fantastically extensive network of public footpaths.
It's really something you don't appreciate until you go somewhere without such a network.
OS doesn't have a topological (=connected, routable) database of public rights of way. The green lines you see drawn on a Landranger map are just that: lines on a map. I don't need to explain how having a routable database would make a project like Slow Ways so much simpler.
OS, of course, doesn't have accessibility information like stiles, gates, or surface quality, which OSM often has.
I love OS maps, but they are increasingly being marginalised to B2B applications (particularly utilities) and keen walkers. Most UK cyclists have migrated to OSM and, judging from people I see out and about here in the Cotswolds, casual walkers are increasingly going that way too.
Another weird thing that happens on OS maps is that some paths are shown on 1:50,000 maps but not on 1:25000!
OpenMap Local and OpenZoomstack are both available as open data, and give an awful lot of what most people are looking for when it comes to map data.