Malt vinegar. Goes on the fish, or the chips? Both?
What else is it good for, I’ll have to pick some up. Old Blighty is a bit of a stretch for me right now, so no fish & chips.
Yes, sprinkle the vinegar on both and/or put in a shallow bowl for dipping both the fish and chips. (And I think you are supposed to eat the fish and chips with your fingers, not knife and fork).)