Yes I agree, although I think it’s been shortened rather than extended. Another neighbour (not connected to issue) remembers in last 30 years seeing water draining onto the road from further down the site, on the reg. Suspects the old farm manager cut it, as it suddenly stopped one day.
See sketch. End point is pipe connected to a tank. Not a septic tank, but likely an old slurry tank from farm yard above. No longer serving original purpose though, just a chamber as far as we know. It has a corrugated roof just covered in soil, under an access track to the field beyond.
And yep, land owner owns everything around us.
Many thanks