It does not, however, appear that the elder Leake commanded a state's ship, and the only service of the King at sea that the lad can have entered was the semi-piratical squadron under Prince Rupert.

In one, in the North Sea, on 20 April 1667, the Princess was engaged with seventeen vessels, apparently Rotterdam privateers, and though hard pressed succeeded in beating them off.

The captain and master were killed, the lieutenant was badly wounded, and the command devolved on Leake, who after a stubborn fight beat them off and brought the ship safely to the Thames.

The Royal Prince was dismasted; many of her guns were dismounted; some four hundred of her men were killed or wounded; Spragge had shifted his flag to the St. George; and a large Dutch ship with two fireships bore down on her, making certain of capturing or of burning her.

He invented also what seems to have been a sort of howitzer, which is spoken of as a "cushee-piece", to fire shell and carcasses; in theory it seemed a formidable arm, but in practice it was found more dangerous to its friends than to its enemies, and never came into general use.