Kingsmill was a contemporary and close friend of Lord Nelson, and was one of the prominent Royal Navy admirals of his time referred to as "The Conquerors of the Seas", illustrated in Piercy Roberts' 1800 engraving.

[1] The outbreak of the Seven Years' War offered further opportunities for advancement, and in February 1761 he was promoted to master and commander of the sloop HMS Swallow.

His capture of the 10-gun French privateer Sultan led to the confirmation of his rank on 3 July, and he soon received an appointment to the bomb vessel HMS Basilisk.

It was during this period that he was recalled and placed in command of one of the yachts preparing to carry Princess Charlotte of Mecklenburg-Strelitz and her suite to England to marry King George III.

[8] His dabbling in politics brought him more enemies in high positions, and Kingsmill was destined to remain without a ship until April 1782, when he took over the newly refitted 74-gun third rate HMS Elizabeth.

[8] Kingsmill was too late to join Admiral Lord Howe's expedition to relieve Gibraltar, and was instead offered command of a reinforcement squadron that was being prepared to sail to the East Indies.

[8][10] He does not appear to have ever spoken in parliament, but records show that he voted in favour of William Pitt over his 1785 Reform Bill, against him during the Regency crises of 1788 and 1789, and against the Duke of Richmond's fortification plans in 1786.

[8] The Nootka Crisis in 1790 brought an end to his career in politics, as Kingsmill returned to active duty in command of the 90-gun HMS Duke.

[8][10][14] The forces at his disposal consisted of two ships of the line, seven frigates and four smaller vessels, which he quickly put to use combating the swarms of enemy cruisers that operated in these waters.

[8] He was advanced to Vice-Admiral of the White on 4 July 1794, and continued to grow rich off the spoils of captured privateers and French supply ships.

Kingsmill knew his forces were too few to risk an open engagement, but shadowed the French fleet, which were eventually dispersed by gales, and was able to harry their retreat back to France.

[8] He was ready for the French when they made another attempt in May 1798, but the crushing of the main force by Sir John Borlase Warren at the Battle of Tory Island put a decisive end to the threat.