Hard to tell what they are as I can't really see the size - they seem to be what are known in the fungi field as "little brown jobs". And little brown jobs are hard to differentiate, especially from a photo.

Yes they do suddenly appear, but it is not from nowhere. The mushrooms that we see above the soil are just the fruiting bodies of much larger underground organisms. Imagine an apple tree flat under the ground and the apples just popping through the earth - that is more or less what is happening with fungi. They can remain dormant for many years until the conditions are exactly right for them.

Probably no way of stopping them spreading but they are very unlikely to do any harm. Foxes, squirrels and even cats are much more fungi aware than humans and won't eat anything bad for them. If you really don't like them, just brush them away. No guarantee that they won't reappear though.

I spend a great deal of time trying to get all sorts of fungi to grow in my garden so I am jealous!

(And by the way, the fact that you might find some of the larger fungi gnawed by deer, squirrels or rabbits is no indication of their safety for human stomachs!)

O.K. Thanks. I agree that they are quite cool but was just a little concerned for wildlife and neighbours' pet cats.

Don't worry, I have NO INTENTION of picking and eating.

I am not in to mushrooms from the supermarket and certainly would not eat any growing in my garden, unless I was willing to be rushed in an ambulace to A&E (Accident & Emergency Department at the Hospital.)

These are really nice aren't they - I love the stripes round the edges. Identification can be very tricky as you often need to see the complete stem by digging it up rather than breaking it off, a section through the cap to see how the gills are attached to the stem, and a spore print. But it is interesting to do a spore print anyway, just for fun. Pick one, remove the cap and lay it gills side down on a sheet of white paper. In case the spores are white you could do two, and put the second one on coloured paper. Leave them for about 24 hours and lift them carefully. You should see a pattern of spores which have been dropped from the gills. Usually they will be white or creamy but not always. Don't worry about poisoning yourself. Few are deadly, and even then you have to eat them first - just wash your hands after handling.