[1] He was a nephew of Vice-Admiral James Gambier and of Admiral Lord Barham[2] and became an uncle of the novelist and travel writer Georgiana Chatterton.

[4] He was taken prisoner for a short period and, after having been exchanged, he was made a post captain on 9 October 1778 and appointed to the 32-gun fifth-rate HMS Raleigh and saw action at the capture of Charleston in May 1780 during the American Revolutionary War.

[2] In February 1793 following the start of the French Revolutionary Wars, Gambier was appointed to command the 74-gun third-rate HMS Defence under Lord Howe.

By faith an evangelical, he was regarded as an intensely religious man, nicknamed Dismal Jimmy, by the men under his command.

[4] As captain of the Defence Gambier saw action at the battle of the Glorious First of June in 1794, gaining the distinction of commanding the first ship to break through the enemy line and subsequently receiving the Naval Gold Medal.

[6][8] In May 1807 Gambier volunteered to command the naval forces, with his flag in the second-rate HMS Prince of Wales, sent as part of the campaign against Copenhagen during the Napoleonic Wars.

Prizes included eighteen ships of the line, twenty-one frigates and brigs and twenty-five gunboats together with a large quantity of naval stores[13] for which he received official thanks from Parliament, and on 3 November 1807 a peerage, becoming Baron Gambier, of Iver in the County of Buckingham.

He called a council of war in which Lord Cochrane was given command of the inshore squadron, and who subsequently led the attack.

Gambier refused to commit the Channel Fleet after Cochrane's attack, using explosion vessels that encouraged the French squadron to warp further into the shallows of the estuary.

Admiral Sir Eliab Harvey, who had commanded "Fighting Temeraire" at the Battle of Trafalgar, believed they had missed an opportunity to inflict further damage upon the French fleet.

[16][17] In 1814 Gambier was part of the team negotiating the Treaty of Ghent, ending the War of 1812 between Britain and the United States.