It is like the beginning of an Edith Wharton novel. Innocent twin sisters aged 29 leave Cape Town and move to London, with their beefcake beaux in tow, hoping to make careers for themselves, only to discover their aristocratic family history catching up with them, as they negotiate a whirl of parties and photo shoots, diamonds and courtesy titles.

As the daughters of an earl, they are Lady Eliza and Lady Amelia, but the more voluble twin, Amelia, shakes her golden head. ‘Only in England. We’ve never heard [the titles] outside the UK. We don’t use them, but people use them to us.’ Eliza offers: ‘We just say, “Call me Eliza, call me Amelia.”’ Similarly, thanks to a new association with Chopard, they are ‘learning a lot’ about fine jewellery because previously, ‘It just wouldn’t have made sense to us with our very outdoors life.’

Sitting around a kitchen table with these two beauties, they seem tender-hearted, frequently breaking off to put reassuring cashmere-clad arms around one another, or to express regret about the rescue cats they left behind in Constantia, the affluent suburb where they grew up. They are the nieces of Diana, Princess of Wales, and use ‘we’ a lot, but it’s not the royal we, it’s the twins’ united ‘we’.

Amelia takes the lead. ‘Cape Town was all about the sea, hiking, horse riding, tennis, netball… After high school and university we were so happy that we didn’t feel the need to move, but the last few years we found our confidence. In London everyone seems so driven; it makes you want to reach your full potential.’ And they have embraced, for example, the theatre, with a visit to The Lion King. ‘There’s nothing like that in Cape Town.’

Eliza, the slightly less chatty twin, chips in, her voice identical to her sister’s – gently South African with an English twist. ‘This is our home too. We always came here three times a year to see our father. We’d come to London, but we’d mainly stay at Althorp [the Spencer family seat and 13,000-acre estate] because it’s easier having children in the countryside, isn’t it?’

Their parents, Charles Spencer (bestselling history writer and guardian of Althorp) and Victoria Lockwood (British model and former face of Ralph Lauren) divorced in 1997, when the twins were five, the same year Diana died. Understandably, their memories of her are slight, but they have previously said how she ‘always made an effort to connect with us… and had a talent for reading children’s hearts’. In one memorable incident on a beach, she made evading the press into a game for them, asking who could race to the car first.

Living in Cape Town spared them the intense interest they would have endured here. ‘We were so lucky to have a normal, relaxed childhood. Public scrutiny didn’t exist at all,’ says Eliza. ‘You don’t really see photographers or journalists in Cape Town; it wouldn’t have been particularly relevant or interesting.’ Did people not know about their family, or pretended not to know? ‘Definitely people at school knew there was some kind of tension, but as much as some people might be interested, they never brought it up.’ School days ended at 2pm, and afternoons might be spent volunteering at a local crèche for orphans, ‘just giving them love’.

‘We were surrounded by a lot of poverty in Cape Town,’ says Amelia, remembering how, like young Jilly Cooper heroines, they would go round the streets selling their juvenile artwork to raise money for food for stray cats and dogs. ‘We already had eight rescue cats, a pug and a Jack Russell when I fell in love with Eliot – he’s my black-and-white cat. He was born in a bin. When I first put him on my shoulder, his little claws just wouldn’t let go… I hid him for a week from my mother.’

Their philanthropic interests in diamond-rich South Africa make them supersensitive to Chopard’s credentials. ‘We’re very grateful to be able to wear jewellery that takes ethics and sustainability into consideration.’

Eliza remembers weekends spent camping off-grid in Cederberg ‘with my mother and her partner [her now ex-husband, South African businessman Jonathan Aitken]. We’d wear head torches and make hot chocolate.’ Their mother, now 56, who once struggled with drugs and anorexia, cuts an elegant figure. ‘[She] has incredible style. Our house was very homey, quite traditional, a comfortable home for five children [the girls have two younger brothers, Louis, Viscount Althorp, and Samuel Aitken]. My mother never puts any emphasis on brands or make-up; she’s just so natural.’

Their father is less present in their conversation, his absence from their sister Lady Kitty Spencer’s lavish wedding in Rome this summer, to the South African fashion tycoon Michael Lewis, passing unexplained. When I ask what they like to do with him when they are all together, they refer back to childhood: ‘Football, competitive croquet, hide-and-seek. Growing up, the house would always be busy, full of extended family and friends.’ They would spend every other Christmas at Althorp, shocked by the cold: ‘A quick walk, then church, lots of food, just a relaxed family day.’ Does the Earl discuss his work as a historian with them? ‘Well, growing up he used to tell us about that at Althorp,’ Amelia says. ‘Maybe it wasn’t too age-appropriate,’ mutters Eliza. Too difficult? ‘I haven’t actually read his latest book [The White Ship, about the naval disaster which claimed Henry I’s heir] but I’m sure we will get round to that,’ says Amelia.

Working as a wedding planner, Amelia has managed over 40 nuptials in Cape Town. ‘I’m a romantic,’ she admits. ‘I love the structure of wedding planning, the timeline. I’m a people person. I enjoy working with everyone from the bride and groom to the parents.’ For her sister Kitty’s wedding, planned thousands of miles away in lockdown, her role was just ‘sisterly advice’. ‘Sarah Haywood [the pre-eminent designer of every mogul’s special day] planned Kitty’s, and she’s very talented.’ When it comes to her own wedding, to fiancé Greg Mallett, Amelia feels no pressure. ‘That was the dream wedding for Kitty, but I’d be happy with something smaller. We’ve got different tastes.’

Greg relocated with her, and is working from their home in Fulham as a fitness instructor (he is one of the staff of Jeff, an online hub). ‘It’s very motivating being with a fitness instructor,’ she says, laughing. ‘We’ve been together 13 years and it still feels like the first year.’ Eliza’s sweetheart of the past three years, Channing Millerd, is CEO of a blockchain-solutions company, tracking and tracing beef worldwide. ‘It’s a world which I don’t understand too well, but it’s very exciting.’ Eliza, already a graduate in psychology and criminology, studied interior design in lockdown and wants to work creating contemporary interiors.