I thought one reason to walk s/n for mere mortals was that you had walked yourself fitter before tackling cross fell and the Cheviots. As this obviously doesn't apply to ultra runners, is there something to be said for getting the more challenging bits done first while a bit fresher?
Mind you I found the first day over Kinder quite hard. My excuse is that the pre walk training I had intended to do was messed up by eating a dodgy langoustine at a party.