Thanks Wold Ranger.
That suggests to me that someone like Matt Giles or Jez Bragg (both have done Round Rotherham in about 6h18m) could look towards a 6 hour Green Man (with Green Man being 3-4 miles shorter and the same amount of ascent: I can't imagine the terrain's that different). Hence there must be quite a lot of scope for getting the record down (especially with good support).