My sainted mum was of untarnished working-class blood — she worked, variously, as a cleaner, factory hand and shop assistant — and like most women of her kind who grew up before the 1960s, she never swore. Not a ‘bitch’, ‘slut’ or ‘slag’ ever passed her lips, though she certainly loathed a lot of women and always had at least two feuds on the go. In her eyes, using words like that would have made her just as bad as the targets of her disapproval. No, her ultimate diss for females she disliked was ‘Lady Muck’.

It’s a delightfully descriptive phrase and, having heard a lot from both Emily Thornberry and Emma Thompson recently, I’m surprised it isn’t more popular, because Lady Mucks move among us as much as ever today. The Cambridge Dictionary defines the type as ‘A woman who thinks she is very important and should be treated better than everyone else’ and you’ll know her when you see her — or even better, hear her. That voice! That oleaginous, am-I-speaking-slowly-enough-for-you-thick-little-plebs-to-understand, more-in-sorrow-than-in-anger voice.

In politics, you can currently hear this voice from the two most prominent Lady Mucks in the Commons (how the name of their workplace must pain them!). Diane Abbott, with her vast pomposity, hypocrisy and sense of entitlement, has shown us that women of all hues can make it to Lady Muck status, whereas previously many of us presumed it was a white woman thing. But if Abbott is something of a busted flush on the opposition benches, her sister under the hyper-sensitive skin, Emily Thornberry (aka Lady Nugee — two times a lady, then) is surely a rising star, despite her forced resignation a few years back for the fantastically Muckist act of tweeting a working-class driveway displaying the England flag and a white van during a by-election in Kent, for all the world as though she had spotted a fascinating new species of sub-human being. Even Ed Miliband, hardly a horny-handed Lawrentian son of the soil, opined that it conveyed ‘a sense of disrespect’. Thornberry, with great slipperiness (being Lady Muck means never having to saying one is sorry) countered that she was raised on a council estate by a single mother. Her goose looked cooked when it turned out that, Cinderella-style, her father was a hugely successful lawyer who rose to become assistant secretary-general of the United Nations and that she had in turned married a knight and gone on to live in a £3 million townhouse. It took the rise of her comrade-in-chameleonism Jeremy Corbyn to reinstate this chav-mocking Marie Antoinette to her rightful place.

You’d expect the Tory benches to have their share — Tory Lady used to be practically interchangeable with Lady Muck — but they’re increasingly down to earth. Mrs May is too shy to be a Lady Muck, Ruth Davidson too bouncy. Mrs Thatcher acquired a Lady Muck voice through elocution, rising through the Tory ranks when they were still hideously snobbish, but was far too energetic and ideological to qualify. No, Lady Mucks are far more likely to be found on the left wing, and it’s not a new thing; you can trace the lefty Lady Mucks right back through Lady Antonia Fraser to the Fabians and the Bloomsbury Group. The ghastly snobbishness and anti-Semitism of Virginia Woolf and Vita Sackville-West have been well documented and satirised. But it’s shocking to discover that the Fabian society, as well as the birth control pioneer Marie Stopes, supported forced sterilisation. (Eugenics is the ultimate Lady Muck scientific theory — though the poor dolts never seem to notice that if the dull-minded and idle really were stopped from breeding, they’d surely be the last of their lines.)

E.M. Forster nailed the type brilliantly with his portrayal of the shocking Schlegel sisters, intellectual Lady Mucks imposing their air-headedness earnestness on those below and above them on the social scale. How appropriate that Emma Thompson was cast as Margaret Schlegel in the film of Howards End; whether signing petitions in support of Roman Polanski or telling us how to vote in the Brexit referendum, she is the foremost Lady Muck of Luvviedom.

But Lady Mucks aren’t just left-wing; Princess Margaret was the ultimate LM of modern times, allegedly looking down even on her own mother and gran as they had no royal blood. The Princess of Wales didn’t have a trace of the condition — on the contrary, it was only contact with those less fortunate that made her feel useful — and it is said that Her Majesty the Queen doesn’t differentiate between us lesser mortals. Sarah Ferguson, however, is a magnificent example of what happens when Lady Muck meets New Age Flake. I’ve also known prostitutes who talk about ‘chavs’ and complain that they catch nasty viruses from hoi polloi if ever forced to use public transport — the type popularly known as ‘all fur coat and no knickers’. Camila Batmanghelidjh is the ultimate right-on Lady Muck. Younger hopefuls can be identified by their clean-eating habits and ‘blessed’ hashtags: anything that sets them above the rest of us. You’re actually more likely to find them in Shoreditch than Surrey these days; think of the recent fuss when the artist Hetty Douglas posted a snap of three scaffolders in McDonald’s with the caption ‘They look like they got one GCSE’.

They’ve been the stuff of entertainment for ever: Hyacinth Bouquet and Mrs Slocombe on TV, Lynda Snell on the radio, all over literature, but they are pleasingly rare among actual entertainers, with the odd exception such as the aforementioned Emma Thompson, or Elizabeth Hurley, whose labelling of non-celebrities as ‘civilians’ will forever mark her out as an LM no matter how many times she gets her baps out to flog bikinis. A diva is not a Lady Muck, no matter how demanding (Streisand, Callas, Garland, Carey, Lopez) because her talent makes her rare. Lady Mucks are essentially very mediocre women who want to feel special.

This is how you’ll know her — a woman who is convinced she is better than others with no evidence to show for it, no more beauty or wit or humanitarian acts. Above all, she will never judge or mock herself, but lives in order to do so to others. In the age of Brexit, this minor monster has been given a new lease of life.