John Julius Norwich once said to me about his father Duff Cooper, who married Lady Diana Manners (and who was friends with the Duke and Duchess of Windsor): “My Papa had an extremely good reputation for womanising.”

It was expected, explained Lord Norwich, that bed-hopping happened in aristocratic circles and, at house parties where corridor creeping was de rigueur, guest rooms were chosen and positioned with the illicit – or not so illicit – affair in mind. Perhaps part of the reason for their relaxed attitude to sex is all that stately space. For those of us without east wings, multiple guest bedrooms, second staircases and sprawling parkland with follies for frolicking in, adultery is more complicated to achieve.

In the Georgian and Edwardian eras, when many of these stunning piles were built, the aristocracy took a relaxed approach to sex. It was Jane Austen’s characters, reflecting the respectable middle classes, who behaved primly. A few years ago, the British Library bought the personal papers of the influential Granville family, which had been kept in sealed boxes in their London home, Devonshire House, since the early 19th century. Among the revelations was a forthright letter sent in 1809 to Harriet Granville, daughter of the celebrated socialite Georgiana, Duchess of Devonshire, which seems to sum up the mores of the day. Written by her aunt, (also called Harriet) it informs the younger Harriet that her dashing new husband, Viscount Duncannon, later third Earl of Bessborough, is her aunt’s former lover and father of her two illegitimate children.

Meanwhile, Harriet may have married Viscount Duncannon aged 19 but, throughout her marriage, she conducted a 17-year love affair with Lord Granville Leveson-Gower, a dandy with brilliant blue eyes. In tight society circles, everybody is intertwined and such letters reflect women trapped in their marriages, while their illegitimate children were being brought up elsewhere.