What kind of caterpillar is this?

What kind of caterpillar is this?

Observation - What kind of caterpillar is this? - UK and Ireland. Description: Orange-brown caterpillar with black spots by the spiracles. Lighter, flesh-coloured head. 4 pairs of abdominal prolegs, 1 pair of anal prolegs. Around 5cm in length. Found under a log in back garden, possibly having over-wintered there?

Orange-brown caterpillar with black spots by the spiracles. Lighter, flesh-coloured head. 4 pairs of abdominal prolegs, 1 pair of anal prolegs. Around 5cm in length. Found under a log in back garden, possibly having over-wintered there?