Hi Phil, This track is still there, and features on the old maps (Bartholemews 1940s-1960s) of the estate. There are historic walk routes here, and once Ive bee over there in the nexct few days (it's in my village), I'll re-survey it, as I haven't been there in a few years, to be fair. 
The Hafod Estate walks are of archaeological significance, and certain routes are important to denote for preservingf of village traditions (I have local funding to preserve these original walks as part of local culture).
This is an area of specialism I trained in, specifically here, and I'm aware of the critical scholarship of this area. Any suggestions on marking "ruined" footpaths very welcome. I shall get a GPX if you think that necessary.
Thanks so much for watching over the edits (and picking up the duplicate waterfall too - I thought I'd deleted the other one). Much appreciated.
Best,
Rupert