[4][5] He was assigned to the Channel Fleet under Admiral William Cornwallis, and on 10 August 1805 he came across the 40-gun French frigate Didon off Cape Finisterre.

[4][6] Prior to the sighting Phoenix had intercepted an American merchant, en route from Bordeaux to the United States.

Didon, which was carrying despatches instructing Rear-Admiral Zacharie Allemand's five ships of the line to unite with the combined Franco-Spanish fleet under Vice-Admiral Pierre-Charles Villeneuve, intercepted the American merchant and from him received news that a 20-gun British ship was at sea and might be foolish enough to attack Didon.

[7] Phoenix ranged up alongside Didon and engaged within pistol shot but was to far windward and having too much way upon her soon drew ahead of the French ship.

[6][9] The following day the combined fleet under Villeneuve, heading for Brest and then on to Boulogne to escort the French invasion forces across the Channel sighted the three British ships.

'[10] Villeneuve's failure to press north was a decisive point of the Trafalgar Campaign as far as the invasion of England went, for abandoning all hope of fulfilling his plans to secure control of the Channel Napoleon gathered the Armée d'Angleterre, now renamed the Grande Armée, and headed east to attack the Austrians in the Ulm Campaign.

[10][12] The British ships altered their course and made for Plymouth, where they arrived on 3 September, having prevented an attempt by their French prisoners to capture Phoenix and retake Didon.