THE Mitford Sisters are back in the news with the announcement that an adaptation of Nancy Mitford's 1945 novel The Pursuit of Love, starring Lily James, Dominic West and Andrew Scott, is to be the new BBC drama on Sunday night in the spot vacated by Line of Duty.

The Pursuit of Love? Are there any cops in it?

Not this time. Set in Europe between the wars and closely modelled on Nancy Mitford's own life, it's the story of Linda Radlett, the most beautiful daughter of an eccentric aristocratic English family led by a domineering racist misogynist (played in the TV adaptation by West). Linda goes in pursuit of the perfect husband before falling for a French duke. Mitford herself had a relationship with Gaton Palewski, a Free French commander and politician.

Who were the Mitfords?

English aristocracy. Their parents were Lord and Lady Redesdale, who had seven children (six girls and a boy) who mostly grew up to become social gadflies.

Come to think of it, was one of them not a Nazi? Not Nancy, I hope.

Ah, no, you are thinking of Unity. Most of the Mitford children met Hitler but Unity was the one who was closest to him. She used to sign off letters "Heil Hitler!" Love Bobo."

Diana Mitford also married Oswald Mosley, leader of the British Union of Fascists, in Goebbels' drawing room with Hitler as a guest.

So they were posh English fascists?

Well, they were all posh and terribly snobbish but not all were fascists. Decca ran away to become a communist. She was known as the "red sheep" of the family.

They sound lovely. Any redeeming features?

Nancy, the eldest, was a novelist and a wit. Deborah became a duchess and the public face of Chatsworth House.

Why do we care?

Well, there's a question. The sisters knew everybody who was anybody in the middle of the 20th century and recorded their encounters in both their letters to each other. Deborah, Diana and Jessica all published books, and Nancy's novels are quite highly regarded, though the novelist Andrew O'Hagan once offered the backhanded compliment: "If she had cared more about the lives of others she couldn't have written as she did."

Isn't this obsession just another example of our forelock-tugging towards rich people?

It's an argument. Nostalgia for the British upper-class is a real thing in British culture, as can be seen in everything from our obsession with the Mitfords to Downton Abbey. It might also explain how someone as clearly incapable as Boris Johnson ends up in Number 10.

Here endeth the party political broadcast. When is The Pursuit of Love on telly, then?

It starts on BBC One this Sunday at 9pm.