Caterpillar for ID

Caterpillar for ID

Observation - Caterpillar for ID - UK and Ireland. Description: This was biggish, about 55mm long, and was found in a valley bog, on grass beside Marsh Lousewort. Any ideas?

This was biggish, about 55mm long, and was found in a valley bog, on grass beside Marsh Lousewort. Any ideas?