‘I looked at a picture of him today and thought: “Why are you wearing those expensive clothes, you twit?”’ Plum Sykes is in the Claridge’s ArtSpace Café, eating the avocado on toast and talking about Rishi Sunak. ‘He looks like he’s wearing handmade shoes, which is a real no-no – a real no-no! But he can’t stop himself.’

David Cameron would never be so gauche, says Plum. ‘In fact, I remember asking David about that and he said he’d never wear a custom-made suit on the campaign trail because it sends the wrong message.’ Plum quite likes Sunak ‘because he’s clever and sensible’. But she thought Cameron was ‘brilliant – Lord Cameron of Chipping Norton now, isn’t that the funniest thing?’

Plum insists she’s ‘not political at all’. As an aristocratic ‘it girl’ who became a contributing editor to World of Interiors and American Vogue, however, she knows a lot about expensive fashion, rich people and Chipping Norton. Her new novel, Wives Like Us, is an amusing flight of fancy about all three.

It’s set in The Bottoms, a fictional part of the Cotswolds clearly based on the hyper-privileged world of the Camerons, the Jeremy Clarksons, the Bamford estate, the Beckhams and the super-duper rich Americans who’ll pay anything for a slice of idyllic English chic.

Plum wrote the final draft during Covid, when she was ‘reading a lot of P.G. Wodehouse to cheer myself up’. It’s clear that Jeeves and Wooster inspired her – although her Jeeves is an openly gay ‘executive butler’ called Ian Palmer and her Bertie is Tata Hawkins, a cheated-on ‘country princess’.

Today’s uber-rich really do have ‘executive butlers’, Plum explains. It is a ‘very Americanised or you could call it Europeanised version’ of the old-fashioned gentleman’s gentleman. ‘It’s the complete opposite of the sort of butler I remember from my childhood, at my cousin’s house in Yorkshire, who once came into the dining room to serve lunch wearing those plastic glasses with the eyes that sprung out on springs as a practical joke. Today’s super-rich just wouldn’t find that funny. They would think it was rude or that he was drunk.’

Are the plutocrats of the 21st century more stiff, then? ‘Absolutely. They’re much more sophisticated in many ways, but they are not loose.’

‘There’s an aesthetic anxiety,’ she adds. ‘And I think it’s because the money is newer, so it’s a bit like a sort of new version of the Gilded Age in America where it’s all actually rather bourgeois. It’s all about appearances – the opposite of old money, which is about looking like you don’t care about having tons and tons of cash.’

Plum finds traditional English snobbery about what she calls ‘the new nouveau riche’ quite boring. She delights in the way Victoria and David Beckham have been marrying off their offspring to the children of even richer people. ‘That makes them very Gilded Age, doesn’t it?’ she says.

In her own life, Plum has settled with her daughters in Gloucestershire, between Cheltenham and Stroud. ‘My neighbours are farmers who chop logs and things like that. It’s further from London, so it hasn’t been invaded by Londoners and New Yorkers.’

It’s not ‘the dark side’, she says – that rural playground across the A40 with its hedge-funders, its manicured fields and its sushi restaurants. Plum says that she likes ‘dipping into both worlds’, the old money and the new. ‘I’m a bit of a chameleon.’ She finds the Cotswolds scene at once ‘soul-sapping and funny’. As a result, Wives Like Us is more Sex and the City – or Sex and the Shires – than The Code of the Woosters. It mocks its subjects while glamorising them.

The book is also something of a roman à clef, which has made it a huge source of gossip in the area, as members of the real-life Chipping Norton set frantically try to guess which character they might be. ‘It’s hilarious. They’ve all got a new disease I call main-characteritis.’ The truth, Plum says, is that ‘I might take 5 per cent of one person, 5 per cent of another and 5 per cent of another and the rest is my imagination’.

The newspapers are another source of comic inspiration. Matt Hancock’s extra-marital affair was coming out while Plum was writing the book, she points out, raising an eyebrow.

Today, she seems particularly amused by Meghan Markle’s attempt to develop her own ‘American Riviera Orchard’ lifestyle brand. ‘We’re just not sure if it’s authentic. Is that really her Orchard? Or it is just owned by some hedge-fund guy?’

Plum understands brands. Her friend Gela Nash-Taylor, who built the hugely successful clothes business Juicy Couture, told her: ‘A brand isn’t a thing, it’s a person you want to be.’ Plum adds: ‘People want to be Martha Stewart. They want to be Carole Bamford. I’m not sure they want to be Meghan Markle.’

Perhaps in her next novel Plum might take aim at the rich and famous of California. Imagine: an increasingly desperate duchess mingles with an Indian billionairess and her embarrassing husband, the recently deposed prime minister of the United Kingdom.