In the glittering world of Regency London, Mary Anne Clarke had beauty, brains and wit -- but no money.

Spurred on by the demands of a drunken husband, a wastrel brother and four children, she chose an exacting profession, aimed for the top -- and soon became the mistress of the Duke of York.

For her family she raised a fortune by selling military commissions. The scandal rocked the country from palace to Parliament. The Duke was disgraced, the Royal Family shamed...