Master James Keith’s HMS Neptune followed HMS Temeraire and Nelson’s flagship at the van of the admiral’s line at Trafalgar.

The three-decker of 98 guns was one of the newer ships in Nelson’s fleet, having entered service eight years earlier. Crewed by more than 700 men, she was led by Capt Thomas Fremantle, an officer very much after Nelson’s own heart.

As Neptune readied for battle, Fremantle summoned his men for a brief rallying call, as recorded by sailor James Martin, one of the few from the lower decks who has left an account of Trafalgar.

“If he fall,” Martin noted Fremantle’s exhortation in halting English, “he fall Covred with Glory and Honnor and Morned by a Greatfull Country the Brave Live Gloryous and Lemented Die.”

Shortly before 2pm, battle was joined as Neptune passed under the stern of the French Bucentaure. She was “raked by the enemy”, Midshipman William Badcock recalled. “The whole of the crew, with the exception of the officers, were made to lie flat on the deck. Had it not been for the precaution, many lives must have been sacrificed.”

Despite being damaged by Bucentaure, Neptune delivered a broadside into the Frenchman, then continued along the starboard of Spain’s Santisima Trinidad, with which she would grapple until the battle was won.

Mid Badcock looked admiringly at her bow “splendidly ornamented with a colossal group of figures, painted white, representing the Holy Trinity from which she too her name. Her lofty, towering sails looked beautiful, peering through the smoke as she awaited the onset.”

But this was no time for mercy. Neptune’s guns reaped a terrible harvest on their Spanish quarry, as one Spanish sailor recalled. “We were surrounded by the enemy, whose guns kept up a tornado of round shot and grape shot on our ship.

“Blood ran in streams about the deck, and in spite of the sand, the rolling of the ship carried it hither and thither until it made strange patterns on the planks.

“There was hardly a man to be seen who did not bear marks, more or less severe, of the enemy’s iron and lead.”

After Santisima Trinidad struck her flag, William Badcock went aboard his prize to round up Spanish prisoners. “Her beams were covered with Blood, Brains and pieces of Flesh and the after part of her Decks with wounded, some without legs and some without an Arm.”

Neptune’s losses, despite the ship’s masts and sails taking a fearful battering, were remarkably light: 44 killed and wounded.

The greatest loss was the death of Nelson. Five days after the battle, Neptune’s captain finally found time to scribble a few words to his wife Betsy. “This last Week has been a scene of Anxiety and fatigue beyond any I have ever experienced. The loss of Nelson is a death blow – I am well aware that I shall never cease to lament his loss whilst I live.”

Two centuries on, the name Neptune remains in the van of Royal Navy life. The name in 2005 is carried by HM Naval Base Clyde, home to Britain’s ultimate deterrent, the Trident missile nuclear submarine fleet.