http://blogs.spectator.co.uk/coffeeh...we-support-it/
DB: Why are you supporting AV?
NF: Well, first past the post is finished, it doesn’t work.
DB: Why?
NF: It doesn’t really have legitimacy. You know, it worked when we were a two party state. I completely lost faith in it in 2005 when Blair was returned with a 60 seat majority on 36 per cent of the vote, or 22 per cent if you factor in low turnout.
I’d always argued that we needed FPTP because it gave us strong government and we mustn’t become like Italy. 2005 put a torpedo through that for me. It’s bust.
Basically he didn't do as well as he wanted so changed his views even though the situation behind his original views hadn't changed at all :P