No Captain can do very wrong if he places his Ship alongside that of the Enemy

Horatio Nelson

Nelson sent a copy of the memorandum outlining his tactics to every ship in his fleet.

This copy signed by Horatio Nelson and headed "Victory Off Cadiz 9th October 1805" is thought to be of particular interest because it was issued to Captain Eliab Harvey of The Temeraire.

The ship, which was to be The Victory's companion in battle, is well known today because of a painting by J M W Turner which hangs in the National Gallery.

Felix Pryor, manuscript consultant of Bonhams book department, said: "The Temeraire has become almost mythical because of Turner's painting.

This letter could raise up to �60,000

"It must be the most famous picture ever of a ship.

"This document will remind people that The Temeraire was in reality an important fighting ship that, together with The Victory, was the first to break the enemy line at the Battle of Trafalgar."

The memo explained to Captain Harvey that the Admiral planned to avoid the old-fashioned linear battle formation and instead divide his fleet into three squadrons or divisions.

The document begins: "Thinking it almost impossible to bring a Fleet of forty sail of Line into a Line of Battle. Without such a loss of time that the opportunity would probably be lost of bringing the Enemy to Battle in such a manner as to make the business decisive, I have therefore made up my mind".

Nelson also advised that "No Captain can do very wrong if he places his Ship alongside that of the Enemy".