The Galatée had been sailing from Bordeaux to Quebec when a British ship, the Essex, captured it. The French ship was taken to Portsmouth and sold. Its crew was locked up.
It was part of a plan. In the Seven Years' War, France had fine ships but too few experienced sailors, so Britain imprisoned as many as it could. In 1758, 19,632 of France's 60,137 sailors were being held in Britain, about a third of them.
Some died of disease and hunger. Many others were eventually released.