By no means an unusual species, this is listed in some of my books as P. hydrophilia.
It seems to favour growing on Oak in the wood, but I'm sure it's found on other deciduous species.
There were over 50 fb's in this single troop.
I was pleased to be able to get a good photo of the partial veil still covering some of the gills. As the caps expands they will soon disappear, with perhaps just a few fragments remaining around the edge of the cap.
As the caps age they gradually fade to a creamy colour (like those in the centre of this group).
For some reason the slugs don't seem particularly partial to them, so I often come across older specimens of them.