Incidentally, there's a statutory declaration at https://www.hertfordshire.gov.uk/media-library/documents/environment-and-planning/countryside-access-and-management/rights-of-way/applications/landowner-deposits/register-of-landowner-deposits/n/north-mymms-rvc-hawkshead.pdf which to the best of my understanding confirms that this path *is* a public footpath (despite the further comment that there are no other public footpaths on the land). 