fisherman’s half
When you’ve still got half a pint left but your mate offers you a drink and you don’t want to miss out, so you get a half pint with which to top up the glass. A common scenario since the decline of the fishing industry, so fishermen sit at a ‘spoons nursing a pint instead of fishing.
Ray: Want a pint mate?
Hank: Still got half, I’ll take a fisherman’s half
Hank: Still got half, I’ll take a fisherman’s half