If you buy a fish sandwich in Britain today you can be fairly sure it will not contain thunnus thynnus, otherwise known as the Atlantic bluefin tuna.
Overfishing means these zeppelin-shaped leviathans – they can grow to a length of four metres – are severely threatened, so serving them up has become taboo.
But there is a different attitude in Japan, where the bluefin is prized for sushi and sashimi, despite its endangered status. Up to 80% of the Mediterranean bluefin catch travels thousands of miles to the east, says Julie Cator of marine campaign group Oceana. For the Japanese, continued consumption of bluefin is a “cultural issue”.