‘Each morning I stare at our sturgeons for 10 minutes, which brings me energy,’ says head of R&D, Bastien Debeuf, as a submarine-like fish skims the cool pool in our midst.

Its head is a kind of shield, and its scale-free body a suit of armour against all but human predators. His mascot dog, Jam, joins in. ‘He’s fond of caviar and often eats some during fish sorting,’ says Debeuf. ‘We think that’s why he’s lived so long…’

Debeuf shares the legend of a Russian princess. ‘On visiting the Gironde river in France she was so shocked to see fishermen discarding a sturgeon’s eggs in favour of the meat that she showed them how to extract and salt them.’ That was in the 1920s, although the earliest written records of caviar date from Batu Khan, Genghis Khan’s grandson.

Traditionally, Russia and Iran were the leading producers, but dwindling stocks saw all sturgeon species regulated in the late 1990s and growth in caviar farms, including Sturia here in Bordeaux.

Best eaten from mother-of-pearl spoons, Sturia’s caviars are glossy, fresh and long-lived in taste. Available from Harrods, they include supple Classic (£60/ 30g), nutty, assertive Origin (£75/ 30g) and firm Oscietra (£84/ 30g).from the revered Siberian sturgeon, Acipenser Gueldenstaedtii.