A signed letter from Lord Nelson to his mistress, Lady Emma Hamilton, has beaten its estimate by 150% at a Bonhams auction.

The circa 1801-1802 letter, written at the height of their affair, sold for £20,000 ($31,755) against an £8,000 high estimate at the Books, Maps, Manuscripts and Photographs sale in London on November 13.

"I shall not come to your house after what passed last night"

The billet-doux, scribed shortly after his victorious return from the Battle of the Nile, refers to a disagreement between the lovers the previous evening, and makes clear Nelson's intent to defend Hamilton's integrity as the scandal became the talk of the country.

"I shall not come to your house after what passed last night 'till you send for me when I shall fly," he wrote, adding: "Never will I sit tamely and see you my dear friend neglected or insulted".

Its highly charged content and the enduring fascination with Nelson and his mistress ensured its strong price, as predicted on these very pages.

Nelson signed letters are growing in value at a rate of 14.87% pa - you can capitalise on the market today with this incredible item.

Nelson begged Hamilton to burn the letters he sent her. She refused, publishing them in 1814, nine years after his death at the Battle of Trafalgar.

Nelson and Lady Hamilton began their affair in 1899. Within two years Hamilton bore Nelson a child.

Despite pleas from his wife, Nelson continued to live with Lady Hamilton until his death.

One of the last letters that Lady Hamilton sent to Nelson sold for $68,500 earlier this month, achieving a 280.5% increase on its $18,000 high estimate.

Yesterday's auction also featured a superb Elizabethan manuscript, signed by leading figures of the day, which beat its estimate by 212%.