[1] She was the first man-of-war launched since the Act of Union 1800 created the United Kingdom of Great Britain and Ireland, and at her head displayed a lion couchant on a scroll bearing the Royal arms as emblazoned on the Standard.

The following day, due to the exertions of Mr Peake, the builder, and the artificers of the dockyard, she was completely coppered in six hours and on Monday morning she went out of dock for rigging and fitting.

He was superseded that month by George Reynolds, who, in turn, was replaced in December that year by Edward Rotheram, who stayed as flag captain to Admiral Cuthbert Collingwood until just before Trafalgar.

Before they could depart; however, Horatio Nelson arrived from the Mediterranean Sea in pursuit of the French, and Dreadnought proceeded to Cádiz for Collingwood to command a close blockade there.

Early in October 1805, Captain John Conn assumed command of Dreadnought, after having brought Royal Sovereign out from England for Vice-Admiral Collingwood.

Collingwood and Rotheram then moved to the newly recoppered first rate on 10 October 1805, leaving Conn in command of the now sluggish Dreadnought, with her barnacled hull badly in need of careening, but nevertheless with a well exercised ship's company, who for months having been under Collingwood's watchful eye, now contained the most efficient gun crews in the fleet.

She started firing on San Juan Nepomuceno at two o'clock and fifteen minutes later ran her on board and forced her to surrender after her commander Commodore Cosme Damian de Churruca y Elorza had been killed in action.

On 25 November, Thunderer detained the Ragusan ship Nemesis, which was sailing from Isle de France to Leghorn, Italy, with a cargo of spice, indigo dye, and other goods.

[2] On 9 November Dreadnought, Gibraltar, Christian VII, Milford, Naiad, Unicorn, and the hired armed cutters Nimrod and Adrian were all in sight when the Ballahoo class schooner Snapper captured the French brig Modeste.

However, the success was bought at a cost of six dead, 31 wounded and six missing, as well as two ship’s boats, as a result of an ambush by a large party of French troops with two field guns on a cliff overlooking the anchorage.