Mitford sisters in letters

When Jessica Mitford died in 1996 she left her postman £5,000. After a lifetime of letter writing, the socialite knew she had kept him busier than most. The 12,000 letters sent between the Mitford sisters throughout the 20th century have become infamous as a chronicle both of a unique family and of a complicated and politically charged era.

Charting the lives of six privileged and glamorous siblings who moved in the same circles as Churchill, Kennedy, Hitler and Evelyn Waugh, their correspondence is a glittering paper trail of a kind of aristocratic life that no longer exists.

A new collection of the sisters' letters has just been published, edited by Charlotte Mosley, daughter-in-law to Mitford sister Diana, who married fascist politician Oswald Mosley.

The author spent four years collecting the sisters' four million words into her book, The Mitfords. Since the letters are littered with in-jokes, slang and nicknames, copious footnotes are needed.

Without pausing to reflect, Nancy, Pamela, Diana, Unity, Jessica and Deborah describe their extraordinary experiences with a happy acceptance born of privilege.

"They took it for granted that they had a certain position in society," explains Charlotte. "Even if they were shy, and certainly Deborah and Unity were shy as children, when they grew up they could walk into any room and feel comfortable."

The six daughters of 2nd Baron Redesdale did not grow up in luxury, but lived in "relative isolation" at Swinbrook, near Burford, received no formal education and their mother used to breed chickens to make money.

But they did have access to a well-stocked library. Charlotte said: "Both Nancy and Jessica felt at a great disadvantage in later life - that an education would have made it easier for them to make a living - they both wrote terribly well and years of schooling might have ground that out of them."

Over 16 years, the girls were each introduced to society as debutantes. But if Lord Redesdale expected them all to settle down with nice husbands, he was wrong.

Becoming instantly notorious for their beauty, wit and political fervour, almost all the Mitford girls went on to strike dramatic social poses.

Diana 'Honks' left her first husband Bryan Walter Guinness and married the founder of the British Union of Fascists, Oswald Mosley, in a civil ceremony in Joseph Goebbels's drawing room in Berlin in 1936, with Hitler as the only other guest.

Jessica 'Decca' ran away with her journalist husband to support the communists during the Spanish civil war and ended up a journaist in the US.

Unity 'Boud' followed Diana towards fascism. Becoming close to Hitler, she shot herself in the head when Britain declared war on Germany and died an invalid.

Nancy 'Soo' became a socialite and successful novelist, satirising upper-class life in books such as Love In A Cold Climate, which continue to sell well today.

Indeed, only Pamela and Deborah could be described as anything like conventional. Pamela, or 'Woman' was the most rural-minded. She married and divorced physicist Prof Derek Jackson, before devoting her life to raising chickens.

The only remaining Mitford sister, 'Debo', is Duchess of Devonshire, and lives at Chatsworth House in Derbyshire, where most of the sisters' letters are now stored.

Politics deeply divided the sisters as they grew up, explains Charlotte. Diana and Jessica broke off relations in 1937 because of their political differences. Jessica's first husband Esmond Romilly, Winston Churchill's nephew, didn't think fascism was frivolous and more or less cut Decca off from her family.

"In 1969, Jessica and Diana meet again for the first time, and Di writes in her diary about how moving she found it, and how she found all that old love flowing back," says Charlotte.

The Mitfords guilelessly discussed politics in the same breath as shopping. In a letter to Diana dated 1933, 'Debo' writes to express her thanks for a "heavenly evening bag" in the girls' clipped style. "Thank you so much for the HEVERN eveninger, Blor was dumbfounded when Nancy told her what it cost. I honestly never seen anything quite so lovely in all my. I can even forgive you for being a fascist for that. Best love from Debo."

But Charlotte believes the sisters didn't court publicity. "They didn't seek the limelight in the way that celebrities have to now. They had nothing to sell, like a film or pop song. But they were well known because there were six of them and magazines like Tatler and Bystander were devoted to the lives of the aristocracy."

Charlotte herself has successfully avoided media attention, despite marrying Alexander Mosley, the son of Diana and Oswald, and brother of scandal-hit Formula One boss Max.

"My husband Alexander, who died in 2005, was a publisher, but not at all a public person. We were married for 30 years."

Charlotte says she found Diana an "extraordinarily kind, hospitable and generous mother-in-law". "It was very rare to see the sisters together. They didn't hang out in a gang. Pam would come and stay with my mother-in-law from time to time and so would Deborah, but I don't think I ever saw more than three of them at a time.

"Really, the laughter is what you remember. They were always laughing, teasing and joking. It was quite irresistible when you were with them. Very exciting."

* The Mitfords is published by Harper Collins at £10.99.