Hi. Readily agree with your Stropharia suggestion. This looks like one of the blue-green trio, but he wonderful colour is very short-lived and, as here, ‘dullification’ rapidly sets in.
No guarantees of course – it’s fungi – but i’d put money on this being Peppery Roundhead S. pseudocyanea. That fits best for size/the slender build. Aeruginosa and caerulea are usually a bit larger and more robust. The former is also said to be rare/seldom recorded.
Another pointer might be habitat as pseudocyanea seems to prefer grassy places like your location, not parks and gardens, bare soil etc. Churchyards are where i’ve found it most regularly, usually on acid soil (just as Buczacki/Shields/Ovenden predicts).
The fairly strong peppery smell is another thing to check for, hence the common name.
Sorry if you know all this already!
Cheers