That does explain it then, Jon, thank you. When we visited yesterday, there was slight evidence of path usage just near the north end of the way, but with the thick vegetation I'd assumed it was animal tracks - it could well have been the remnants of when the path was used as a permissive bridleway. It would have been impossible for a human to have picked their way through the undergrowth there now, let alone a horse. I did have a good look around for signs, too, and couldn't find anything, so you're probably right with the idea that the scheme ended and the permission got removed.