This is Nick's instrumental guitar piece "Far Leys" (aka "Sketch 1" and "Untitled Original"). I transcribed the version I'm playing from the "Tanworth In Arden II" bootleg LP. Unfortunately, the entire piece was never legally released on any of Nick's albums.

A very truncated version appeared on the 2007 "Family Tree" album as a track called "Sketch 1," and, sadly, only contains the last minute or so of the piece.

Jan 2020 update: I've made the tab available here if anyone wants it: https://www.dropbox.com/s/iclq0b7hh7t...