Large White Caterpillar

This is the caterpillar of the large white butterfly. They were happily eating my Dad's Nastursiums this afternoon, but better that than his runner beans ;) I think it looks a bit like some kind of alien. 

Cowes Week, the big sailing regatta started today. It was a bit too hazy today to get any decent shots, but hey, I've got a week in which to get some :)