Extraordinary fungus!!

We discovered this tree by the river on Paradise Fen on our morning walk. As we approached from the other side we saw patches of this crumbly fungus, but on this side it really seems to have taken hold. We had never seen anything like it, so got out our Mushrooms and Toadstools book once again, and we think it is Laetioporus Suljurious - but we are willing to be put right! It is certainly very yellow!! It is supposed to be edible but we will not check!!