They're neat little holes! If it were autumn, I'd say squirrels, but not sure.

I DO know from bitter experience that it isn't badgers, though! I wonder if anyone else has had this in their lawns?

Dont think Worm casts could it be Voles or even an insect such as a beetle? Although its beginning to look a bit square shaped could there be a drain cover under the turf as well? I have something similar but much much smaller.

Could it be bees or wasps?

Thanks,what i can't understand is there is no removed soil around, and they are fairly deep

By any chance have you used a weedkiller on your lawn? I ask because a few years ago my dad sprayed dandylions growing on his lawn with a systemic weedkiller and the plants died and left holes just like these....just a thought!

there looks to be a few more nearly out of the picture .is it worth sitting and watching the holes for a while ? wear there is a hole as jampot sais theres normaly some soil unless its being carried of .the other option is to get a sharp spade aftet youve made sure its not bees and just dig strate down into the holes and have a look.