Josephine’s intimate letters to Napoleon’s general for auction

In 1806 Josephine Bonaparte wrote to one of Napoleon's most-trusted generals, Alexandre Berthier, who had also become her own close friend, appealing to him to guard the emperor's safety in battle. She could not have known it, but it was her future happiness that was in danger.

"Above all take care of the emperor," she wrote in October 1806 to his chief of staff. "Ensure that he does not expose himself too much, you are one of his oldest friends and it is your attachment to him which calms me."

A few weeks after she wrote so tenderly of Napoleon's welfare, his mistress Eleonore Denuelle would give birth to a son - convincing him that it was his wife's fault, not his, that they had failed to produce the longed-for heir. The fate of their marriage was sealed.

The letter is one of four revealing unpublished letters from Josephine to Berthier - held within his family for more than two centuries - to be auctioned by Sotheby's in Paris today.

The sale also includes orders from Napoleon to Berthier to inspect the defences of ports, towns and camps along the English Channel, before the men visit them together in the following year in preparation for his planned invasion of England.

Josephine de Beauharnais married the considerably younger Napoleon in 1796, to the horror of his family, when he was a young army officer and she was a widow with two small children supported by a string of lovers. She partly befriended Berthier in sympathy for his own irregular household: he was devoted to his married Italian mistress, and she welcomed both of them to her home.