In 1648, during the Civil War, while serving as a captain in the navy of the English Parliament, he prevented the fleet from defecting to the Royalists, and was promoted to General at Sea. In 1651 he served with General at Sea Robert Blake in the capture of the Scilly Isles from Sir John Grenville. Later that year he captured Barbados from Lord Willoughby and the other English colonies in the Americas.
In the First Anglo-Dutch War he was defeated by the Dutch Commodore Michiel de Ruyter at the Battle of Plymouth. Relieved of his command, he went into service in the Swedish Navy, returning after the Restoration of Charles II.
In the Second Anglo-Dutch War he commanded a squadron at the Battle of Lowestoft in 1665. At the Four Days' Battle in 1666 his flagship, the Prince Royal, ran aground on the Galloper Shoal and he was forced to surrender his ship to Lieutenant-Admiral Cornelis Tromp, earning the unfortunate distinction of being the last admiral of the Royal Navy to have been captured by the enemy. He was held prisoner during the war in the Dutch state prison of Loevestein.