Something has been burrowing in my raised carrot bed. A mouse perhaps. The coin is a 2p piece. Will mice burrow to eat carrots?
(http://i2.photobucket.com/albums/y21/meatpaste/hole.jpg)
Bumble bee, perhaps? Lottie ;D
I get lots of holes like that and thought moles as we have plenty of those on the plot, keeping the bl**dy mice company!
Looks very like a mouse - have just spent a couple of days flooding one out of a similar hole (literally, with a hose).
It's on the small side for a mouse, but it's certainly nothing bigger, like a mole. They're quite fussy about where they live, and the molehills couldn't be more obvious. Alternatively it could just be that you dug it over and created a void which is collapsing.