Confidence: It's likely to be this, but I can't be certain.
Notes: At the risk of adding a redundant revision, I fear I have to point out that a typo in the previous ID ('Mitruda' instead of Mitrula) means that this observation doesn't link up with others.
And why haven't I stated my confidence to be "sure as I can be"? Well actually, there are two other near identical species in North America, one of which has been confirmed in Europe and could easily be in Britain. To be absolutely sure, the spores have to be examined. Nevertheless, I have checked the spores of numerous populations, and all so far have been M. paludosa, so this is just me being fussy.
Congratulations to the original poster for the beautiful photographs that show this species well. Alan