I found this mushroom at the end of September, growing at the base of a wooden fence overlooking the sea on the Wirral, UK. It had a strong mushroom smell akin to that of a shop bought mushroom. When the flesh was bruised there was no yellow staining and no aniseed smell.
Can anyone ID it for me please?
It is an Agaricus (I'm 100% certain - I eat those things!). Possibly A.bisporus - i.e. the same species of mushroom you buy at the grocer's store (as you suspected yourself). It is not A. xanthoderma, which by the way doesn't have a pleasant smell and it smells horrible if you cook it - trust me: been there (way back in my innocent youth), done it, got the T-shirt but of course I didn't eat it (I'm only foolish, not stupid).
Thank you for the reply. I left it where it was as I'm a novice where collecting edible Mushrooms are concerned. I've only been brave enough to try Giant puffballs and Parasols so far, things I can't misidentify. I was thrown by the deep marks in the top of the cap, None of the photographs I found on the Internet showed these crevices at all.