I my opinion Fairport has adapted traditional lyrics/tunes to fit their style very well. Dave Pegg's setting of "Polly on the Shore" makes for an effective arrangement (I would steer you towards Martin Carthy, Martin Simpson's or Shirley Collin's versions for their tune variant). In Chicago, the Midnight Special host, Rich Warren, once played Fairport's version of Tam Linn and Michael Cooney's full version together. While Fairport had done a "Reader's Digest" to the lyrics, they kept the spirit of the song without dumbing it down. It takes a singer of great skill, like Michael Cooney, to pull off singing the long version and carry it off.