John was a schoolmaster in Exeter, and family legend maintained that his grandfather had been an illegitimate son of King Louis XIV, although this cannot be verified.

[1] In 1793 the French Revolutionary Wars broke out and Louis was immediately recalled to service to command HMS Cumberland in the Channel Fleet.

In 1794 he moved to the new HMS Minotaur under the command of Admiral MacBride, and participated in the Atlantic campaign of May 1794, narrowly missing the Glorious First of June.

At the battle, Minotaur fought a two-hour duel against Aquilon, ultimately forcing her surrender and there is a possibly apocryphal story that Louis was personally thanked by the seriously wounded Nelson, who is reported to have said "Farewell dear Louis, I shall never forget the obligation I am under to you for your brave and generous conduct; and now, whatever may become of me, my mind is at peace".

[1] In September 1799, Louis, under the command of Thomas Troubridge, participated in operations in conjunction with Neapolitan royal troops, to expel the French from Rome and extinguish the nascent Roman Republic.

The French general Garnier having negotiated a capitulation, Civitavecchia and Corneto were seized by 200 British marines while Louis, with a small party of the Minotaur's crew, rowed up the Tiber and hoisted the Union Flag to fly from Capitol over Rome itself.

[2][3] In 1800, Minotaur was Lord Keith's flagship at the Siege of Genoa and the following year Louis commanded her at the invasion of Egypt.

Less than a year later he was promoted to rear-admiral, raised his flag in the fourth rate HMS Leopard, commanded by Francis Austen, and oversaw 40 small craft seeking to disrupt French invasion preparations at Boulogne.

On 2 October, Nelson dispatched Canopus to Gibraltar to collect supplies for the fleet, despite strenuous objections from Louis that they would miss the forthcoming battle.

[1] Disappointed at these events, Louis was sent under John Thomas Duckworth in late 1805 to pursue a French squadron that had reached the West Indies.