The last surviving Mitford sister is 88 now, but does not look it. Her sight is not as good as it used to be, though, and her voice comes from another time, the Noël Coward vowels shifting between kind but business-like answers and sudden girlish animation. An old-fashioned deference is alive here (her staff call her Her Grace) and I am not the first interviewer to be struck by her impeccable politeness, the kind of forceful politeness that both puts people at their ease and keeps them at a firm arm's length.

It was one of the things she appreciated about her brother-in-law, the fascist leader Oswald Mosley, founder of the British Union of Fascists. "Oh yes, he was one of those marvellous Englishmen who don't exist any more, who had those beautiful manners. It's gone with the wind, and it's thought to be, I don't know, subservient or something - I don't know what it's meant to be - to have good manners. But the fact of the matter is, if you're among people the whole time, it simply oils the wheels of relationships. At least that's what I think. It makes life much pleasanter. I don't mean the sort of manners of getting up when somebody comes into the room, those sort of manners. It's just probably speaking to the most boring person in the room - those sort of good manners. That just doesn't exist anymore. People just go to the one they're interested in." Which, I agree, is quite the best kind of manners. It's just a pity they came with those particular political views.