Revealed: Nelson's sketched blueprint for Trafalgar victory

As the Franco-Spanish fleet sailed out of Cadiz in October 1805 towards the Atlantic swells at Cape Trafalgar, waiting for them, calmly, was a thin, one-armed man, blind in one eye and dressed in a shabby frock coat. Viscount Horatio Nelson hurriedly scratched out a sketch plan – his blueprint for one of the most famous victories in maritime history.

Today,members of the public will be able to see the tattered but hugely significant document when it goes on display for the first time.

The find was made among papers at the National Maritime Museum in London by naval historian Colin White, Director of Trafalgar 200, who is co-ordinating events to mark the bi-centenary of the battle in 2005. He came across the hasty, pen-and-ink drawing on the back of notes Nelson made about promotions and preferments some time before the decisive battle.

"This gives one a sense of looking over Nelson's shoulder as he says: 'Now, this is what I'm going to do'," said Mr White, 50. "Nelson dug the pen into the paper in his excitement: I can sense his presence. It's so much more powerful than the written word, and it's not a case of: 'This is the Battle of Trafalgar, signed Horatio Nelson' – it's a rapid doodle."

The sketch shows the British fleet divided into three parallel lines attacking the French from one side and breaking up their fleet. "I think it will surprise and confound the Enemy," he told Captain Richard Keats a month before the campaign in which Nelson was fatally wounded. "They won't know what I am about. It will bring forward a pell-mell battle and that is what I want."

Mr White believes that the sketch was among notes that Nelson would have taken with him on his many visits to the Admiralty in September 1805. Experts have confirmed that it was made at the same time as the promotion notes. Since these mention Mr Bunce the carpenter and Mr Atkinson the master of Nelson's flagship HMS Victory, they must have been written between 1803 and 1805 when those men were aboard. A footnote adds: "Captain Lydiard wants a frigate." Lydiard did not command a frigate until December 1805.

The sketch will be shown in the Hidden Treasures gallery until moved into a special bicentenary exhibition. One of Mr White's tasks in the Trafalgar 200 project is a detailed study of Nelson's copious letters, many of which have never been published.