Wesley was a pen-name, derived from the family name of Wellesley. She was born Mary Farmar, descended from the Duke of Wellington, and grew up a rebel who believed that she was her mother's least-favourite child. Like many girls of her background, she married for escape; but her first marriage(to Lord Swinfen) was conventional. Her second husband, Eric Siepmann, a writer who never managed to make any money at all, was feckless and bohemian. In between Swinfen and Siepmann, she had a love affair with Czech war-hero, Heinz Ziegler - and possibly with his brother at the same time; and in her later years enjoyed a torrid relationship with Robert Bolt.