Not a great picture (Nick's camera-phone), but any chance anyone can guess the
mushroom identity?
http://comps.org/vicky/mushroom.jpg

It was growing in a tray of flower-seedlings, where I had shoved the packet in
the edge of the soil and it had got damp.

(It's about 1/5" tall, with a slightly shaggy top, nothing of note under the
soil - that's the soil it came from on top of the packet)