Nobu warns diners off blue fin tuna at Berkeley Street and Park Lane

Nobu has placed warnings on its Park Lane and Berkeley Street menus that the blue fin tuna it is offering is "an environmentally threatened species, please ask your server for an alternative".

It's the kind of politically correct non-speak that calls short people "vertically challenged" - when blue fin tuna is in fact on the brink of extinction.

It also appears that in real speak the restaurant is saying is "don't eat our food"

Very strange, and the fact the chain hasn't removed the fish has bemused conservationists. "They shouldn't sell an endangered species. They should change their menu to incorporate a fish that's sustainable", said senior fishers policy officer for WWF, Giles Bartlett.

However, blue fin tuna is one of Nobu's three top-selling fish, and to get rid of it would make a serious dent in profits - that's probably what lies behind this major fudge. And the advice doesn't appear on any other Nobu restaurants around the world, just in London.