Guess What? Don't Know!

I spent a few hours with a neighbour who is tidying an overgrown area of land for a school. It has recently been fenced, to prevent further antisocial behaviour, and to enable school groups to use the area without the threat of dog poo!  My task was to remove a fallen tree, and take away any fallen branches.

Along the way I spotted this fungus on a branch, about 5cms across. I have tried to identify it, but have had conflcting results. If you zoom in then you will be able to see the amazing surface.