this applepie is called a Grannycake coz you're supposed to use Granny Smith apples when baking, but I've tried others and they all work, the cake tastes just as heavenly every time :)
Eddie Izzard has done a funny skit where he mentions Granny Smith apples: http://www.youtube.com/watch?v=B6wKLx2qqiM I LOVE that man!! Seen him live once and got tickets to see him again next year, can't wait!!