Lord Nelson's famous signal ("England expects that every man will do his duty") flies from the Victory (11:50). Turner shows the signal flags flying from the main-mast, though in reality they would have been flown from the mizzen-mast and were replaced with the signal for "engage the enemy more closely" once the battle commenced.
The mizzen-topmast falls (13:00).
The Achille is on fire in the background (late afternoon).
The Redoutable sinks in the foreground (following day).
Tracy, Nicholas. Nelson's Battles: The Art of Victory in the Age of Sail. Chatham Publishing, 1996. (p 194)
Geoffrey Quilley, 'The Battle of the Pictures: Painting the History of Trafalgar', in David Cannadine (ed.), Trafalgar in History: A Battle and its Afterlife, (London: Macmillan, 2006), pages 121-138