Wow Martin - that's Fly Agaric! It's a highly hallucinogenic mushroom, probably the reason why in popular folklore fairies are often depicted sitting on them or dancing around them.
I wouldn't eat that one if I was you. Unless you wish to disappear for a week and emerge having flown over Dover on the back of a pink winged elephant leaving a rainbow trail around Burlington House.
Hang on a mo - did you take a bite out of the smaller one?
