Stropharia caerulea

Common name, the Blue Roundhead

Found this fantastic flash of colour up on the scar today, not one I've seen before.
There are really very few blue fungi, and the only similar one I can find likes dense beech forests, so I'm fairly certain of my identification (happy to be proved wrong/learn more), there's a clear belt (this fungi group get their name from the Greek for belt) on the stem in extras and a marked colour difference above and below it.
I spent a good while stomping around but these three showing early, mid and late stage, we're the only ones to be seen.

Always pays to be looking.