I wonder if it's an Ink Cap mushroom Shirley ? They do tend to split as they get old, and the ones in your photos look like that to me.
Also the stipe (stem) doesn't look as if it has a ring where the cap was attached before opening, as other mushrooms do … and I believe that is characteristic of an Ink Cap Mushroom.
I could be wrong lol

Thanks Hywel, I will look at images of In Cap Mushrooms later on. It seems odd that, 24 hours after mulching with home made compost, those Fungii appeared. Is it a sign of a healthy soil?

Part of the fungus called a mycorrhiza is found under the ground. It is formed of minute filaments which in some way benefit the shrub or other plants it grows in association with.
I don't know if the mycorrhiza of an Inc cap does that, (if indeed this is an Inc cap) but some fungi do. I have seen them sprinkle it on to the soil on Gardener's World programs when they plant certain shrubs.
Heathers in particular benefit from it I think.

Oh yes Hywel, I have seen that added to the hole prior to planting, especially for Roses. I think the worst Fungus I have found in this garden, a few months ago, was a 'Stinkhorn' with the most disgusting smell ... :o((

I thought it was an old specimen of Ink Cap too. You can eat them when they first pop up ( I have ), not much flavour, just sweet.

Oh Feverfew, I'm not a fan of mushrooms, never mind fungii from my garden!

I do like mushrooms, but I only eat the button ones I buy in a supermarket !
I've never seen a stinkhorn. Do they really stink Shirley ?

Definitely! Best described as having a foul smell of carrion or dung ... :o(

The first time I found one in my garden I was unsure of what it was, just knew it needed to be removed. Google it to read more about them Hywel.

Thank you Shirley. I just read that it is edible but somehow I don't think I would like to try it :(

Hywel, I definitely agree with that comment, feeling ill just thinking about it ... :o((

:(

I've eaten them - best with bacon grilled, but not really worth it as they don't have much flavour. and you must pick them before they start to blacken at the bottom.

That's interesting, thanks Stera.

Shirley if you are ever brave enough to try make sure you have a white one. There is another one very similar but brown, also edible but if you drink alcohol with it look out!
Also check up carefully as some of the white ones are very poisonous - these are quite a different shape from those though.

Stera, I never eat mushrooms so thanks, but no thanks!