The English Civil war period (1642-1651) saw a boom in privateering activity in Jersey under the Royalist Governor, Sir George Carteret. Starting with just one galley built in St Malo, Carteret built up his fleet of privateers to about a dozen by arming his prizes. The crews were in the main from foreign parts as the majority of Jerseymen had Parliamentarian sympathies. Technically, this was a pirate operation until December 1644 when Carteret was appointed Vice Admiral of Jersey and, therefore, his privateers assumed a mantle of legality because he could now issue Letters of Marque which allowed the commander of a privately owned vessel to attack enemy shipping either as a reprisal for personal injury or as acts of war. By law privateers had to bring their prizes back to their port of registration which in Jersey was St Aubin where an Admiralty Court decided if it was a lawful prize. As Sir George was not only the private speculator owning the privateers but also the judge he was definitely 'onto a winner', as they say. John Jean in his book "Jersey Sailing Ships" states that 125 prizes were taken and brought back to Jersey in addition to those taken and sold in foreign ports.

Of course, it was not only the Royalist authorities in Jersey which issued Letters of Marque. In 1652 the Parliamentarian Governor of Jersey complained of the actions of large numbers of picaroons, that is free lance privateers, flying the flags of all nations that infested the Channel and held the Island in a stranglehold.