Re: New "world's first" coaster at Alton Towers 2013
^That's been done though (Comet Express at Lotte World). It was never advertised as such though, and nobody really knows about it, so I suppose Alton could do what they did with Air.
Then again, you've got Raptor Attack at Lightwater. Ok, so it's not really underground exactly, but it's sold as that and feels like that.
Either way, Alton can't really get away with the whole "underground" thing as a world's first, when, to all intents and purposes, it wouldn't be the first one even in the UK.