The tale, at least as far as the written version we have, is at least as old as c. 1100 CE, though only the subject matter suggests it is older*. Culhwch is mentioned in a 9th C poem (debatably)*, and a number of Arthur's court as related in the tale are 'Dark Age' heros of the 'Old North' (i.e. before the North of England was lost to the Saxons).