The battle lasted more than six hours and the French suffered over 130 men killed, including the captain and many of the soldiers aboard, before the crew of Amethyst was able to storm and capture Thétis.

Within minutes two additional British vessels arrived, attracted by the sound of gunfire, and helped secure the badly damaged Thétis for the journey to Britain.

Although the French had conquered large swathes of mainland Europe, they were unable to exert any significant influence at sea, where the British Royal Navy had been dominant since the Battle of Trafalgar in October 1805.

[4] The frigate Thétis, stationed to the south of Brest at Lorient, was selected to carry supplies to Martinique and given a full complement of 330 men, 40 cannon and a new captain, Jacques Pinsum.

[6] Both captains were experienced and veteran officers: Seymour had lost an arm at the Glorious First of June 15 years earlier, and they had agreed to hunt together, communicating regularly and with an understanding that all prize money won would be shared equally across both crews.

The frigate, Thétis, replied with her recognition signal and the firing stopped, but the sound had attracted the attention of HMS Amethyst, then approaching Groix from the west.

Seymour was prepared for the manoeuvre and countered it by turning sharply away from Thétis so that the French broadside fell harmlessly into the sea and both frigates performed a complete circle before returning to their previous course.

Amethyst again pulled ahead at 22:05, Seymour successfully crossing the bow of the French ship from port and raking her before swinging back along the starboard side to resume the close range exchange of broadsides.

[10] Thétis began to pull ahead and Pinsum attempted to rake Amethyst in her disorganised state, turning sharply to starboard but coming to a sudden halt as her own mizzenmast collapsed.

[13] In addition, first lieutenant Goddard Blennerhasset was promoted to commander, the junior officers were advanced and Thétis was purchased by the Royal Navy as HMS Brune, the crews of Emerald and Amethyst profiting from the prize money.

[14] Four decades later the battle was among the actions recognised by a clasp attached to the Naval General Service Medal, awarded upon application to all British participants still living in 1847.

Except for one reinforcement frigate, Amphitrite, none of the subsequent French efforts to transport supplies or soldiers to Martinique were successful, and a large British expeditionary force was able to overwhelm the island's poorly-supplied defenders in a brief campaign.

[18] The tightening blockade also affected other French colonies, preventing the despatch of food and military supplies and contributing to the captures of both Île de France and Guadeloupe in 1810.