Thank you for getting back to me. Such holes are classic evidence of skunks, which dig the holes to get at grubs and other underground bugs. However, the only colonies of skunks in the UK have been found in the areas I mentioned above - descendants of released pets. So, we can rule out skunks.
Squirrels will dig holes like that to retrieve a nut they buried previously, so that is one possibility.
A fox could be responsible. When hungry, they will dig for grubs. Voles, rats, and mice dig burrows, not holes. It's possible one of these creatures started to dig a burrow and then decided it wasn't a suitable spot. Here's a site where you can read more about common animal holes found in the UK:http://www.discoverwildlife.com/british-wildlife/how-identify-animal-holes
A squirrel or fox is the most likely culprit. Animals that dog for food often don't return to the same spot. (Skunks are an exception). You may not have a problem at all. If no more holes appear, there's no need to do anything. However, if more holes do show up, the best way to deal with the problem is to trap the animal in a live trap and move it to a more wild area. You can often buy such traps in hardware stores, nurseries, and garden shops. Here is an online source for traps:
If you have more questions, let me know in a REPLY. I hope you've already seen the end of the problem.
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