Hedgehogs can climb surprisingly well actually! It may be these after slugs, snails or insects but it is as likely to be a rodent also. What sort of plants are in the pots?

I've seen video footage of hedgehogs scaling a 5 foot wire mesh fence, so they certainly could manage to scale a 2 foot pot! The other possibility is squirrels - they may be getting at your pots very early in the morning, and you just haven't seen them doing it. If it is squirrels, they're more likely to be burying things like conkers, etc., in the pots at this time of year.

Squirrels go in my pots with the Hazel nuts off our tree but they are sneaky concealers, as they intend to return. We had a community of hedgehogs in the garden at one time but never touched the pots. Fox families,apart from the cubs using them as an assault course. A naughty cat? Who has a 'pot habit'. Maybe you will have to keep watch if you can, who the phantom pot holer is.

thanks all, the plants are a mix of geraniums winter pansies and busy lizzies but nothing in the veg plot where they are also digging

Sounds more and more like squirrels...

It does.