On 21 October 1805, at Trafalgar, Redoutable was located just off the port side of the Bucentaure, flagship of Admiral Pierre-Charles Villeneuve.

As a result of this positioning, Lucas and his crew found themselves between the two columns of British ships commanded by Lord Nelson and in the heat of battle from very early on in the conflict.

Redoutable, however, was still taking on water, and despite the efforts of rescue boats sent over the course of the day, only 119 crewmen were saved before the ship sank with the dead and wounded still on board.

[2] After his release from capture, he was personally awarded the rank of Commandeur of the Legion of Honour by Napoleon for his role during the battle.

[citation needed] After breaching the boom that defended the anchored French fleet, the British sent in fire ships, with Régulus being the first to be attacked.

Régulus ran aground and was in danger of capsizing; trying to save his ship, Lucas threw overboard most of her cannons, keeping only 16 of them together with ammunition and supplies for one month.

Four days later, on 29 April, Lucas managed to patch and refloat his ship, which entered Rochefort to the cheers of the local population.