Beauty in the garden

We have loads of these circling the dead Rowan tree in the garden. I browsed a view related websites but have given up trying to identify these - they don't appear in any of our countryside books either - any ideas?

These beauties are dotted around one section of the garden. They are "shaggy ink cap mushrooms" and are shown here in their various stages of growth starting as fat ovals of "fluffy" white until they grow their stalks, then the tops become a lovely "roof" like this ...


... but within 24 hours it begins to die and shrivel.