The letter, dated March 9, 1816, was written during Napoleon's exile on the island of Saint Helena following his loss at the Battle of Waterloo with the French army in 1815.

The Count of Las Cases was the recipient of Napoleon's letter, which showed the former emperor of France's developing grasp of English.

In the count's book, "Memorial of Saint Helena" Las Cases said Napoleon was writing to him in English in an effort to learn the language of his British captors.

"He sent it sealed to me, I corrected his errors, and replied to him, in English also, by mail," Las Cases said in the book. "He understood the letter, and that convinced him of his progress and proved to him that he could, completely, correspond in his new language."

Even with Las Cases' tutelage, Napolean should probably still be considered a student of the language, as some of the passages can be a bit tricky to decipher:

One passage read, "he shall land above seven day a ship from Europe that we shall give account from anything who this shall have been even to day of first January thousand eight hundred sixteen."

This referred to a ship that would be landing at Saint Helena soon, bringing news of what had happened since January 1, 1816.

Auction house Osenat said there were only three such letters written by Napoleon known to exist in the world.

mz/sej (AFP, AP)