A patch of these large mushrooms was growing in the leafy glade in East Park. Rather like a larger version of the field mushroom, alias the common supermarket mushroom, and reputedly even better to eat.
The fly which features on the first and third pictures certainly seems to think so. I have never tried them. Should you wish to do so, take care not to pick the yellow staining mushroom instead. They come out at about the same time – I am going to post some pictures in a couple of days.