As one of Boris Johnson's key advisers, Cleo Watson has quickly emerged as a vital powerbroker in No 10. Elegant and unflappable, she is one of only a handful of aides who have won the trust of Mr Johnson's dishevelled policy guru Dominic Cummings.
The pair – as The Mail on Sunday revealed last week – are regularly seen striding along Downing Street together and have been affectionately nicknamed 'the gazelle and the pit pony'.
It is little wonder that Cleo, 31, is so driven and successful: she is one of five high-achieving sisters from an extraordinary family whose story could come from the pages of a Jane Austen novel.
The 'Watson girls' enjoyed an idyllic childhood in a 400-year- old country mansion in the Brecon Beacons before forging brilliant careers in politics, business and journalism.
The family at Nell's wedding in 2012. Nell, 34, was head girl at Haberdashers' Monmouth School for Girls, a £30,000-a-year boarding school attended by all five sisters
Indeed, Cleo is the second Watson to work closely with a Tory leader. Her sister Annabel, 41, known as Bee, was Theresa May's Chief of Staff between 2006 and 2010. Molly, the oldest, led an exhilarating career as a journalist in New York before writing a Jilly Cooper-style bodice-ripper novel, while Flora, 38, is a talented gift designer.
Nell, 34, was head girl at Haberdashers' Monmouth School for Girls, a £30,000-a-year boarding school attended by all five sisters. At least three of them studied at Oxford University.
'I certainly remember the Watson girls with great affection,' said Dr Brenda Despontin, who was head at Haberdashers' between 1997 and 2008. 'They were such bright, confident young women, independent, sociable and self-assured. They were always great fun, and brought a great deal to the school.'
The Watson family history oozes achievement. The sisters' grandfather, Vice Admiral Sir Dymock Watson, was a Second World War veteran who later commanded the aircraft carrier HMS Illustrious before being put in charge of British naval forces in the South Atlantic.
Annabel, 41, known as Bee, was Theresa May's Chief of Staff between 2006 and 2010
In the 1950s, he bought Trebinshun House, an elegant Georgian manor house with views of the Black Mountains. Steeped in naval history, it was originally owned by the Hamiltons – a dynasty of swashbuckling Navy commanders that included Admiral Edward Hamilton who became a national hero when he recaptured the British warship Hermione after a mutiny in 1799. Hamilton captained HMS Surprise, the frigate which was depicted in the film Master And Commander, starring Russell Crowe.
The Watson sisters' father, Robin, 72, inherited Trebinshun in the mid-1970s but, faced with its high running costs, converted it into an English language school with his wife Liza, 70. The school helps foreign corporate executives learn the art of small talk and English idioms over dinners in a grand dining room and picnics in the surrounding countryside.
Growing up in a close-knit rural community, the sisters became passionate horse-riders. Strikingly pretty and statuesque – four of the five are about 6ft tall – the Watson girls made quite an impression as they galloped along the narrow Brecon bridleways.
Charles Davies, a 62-year-old venison farmer in Bwlch, near Brecon, recalled how 'you'd see the jaws of lads drop when they came riding by'.
Molly, the oldest, led an exhilarating career as a journalist in New York before writing a Jilly Cooper-style bodice-ripper novel
He added: Everybody stopped what they were doing and watched them go by. They'd ride out with their mother, who passed on her love of horses to the girls. They were all real beauties.
'When they were young, they'd go to local pony clubs, then as they got older and stronger they enjoyed hunting. They'd go to the meets at Brecon regularly.'
It was this love of hunting – and its heady social scene – that in 2004 led Molly to write In The Pink, a racy chronicle of the horsey set that detailed her and her sister Bee's amorous adventures in Ledbury, Herefordshire. After university, Molly forged a successful career as a journalist at the Evening Standard.
She was its New York Correspondent and later recalled 'living off the fat of an expense account, jetting across the States to report on everything from the Oscars to each hanging chad of the Bush/Gore election debacle'.
According to the promotional blurb for In The Pink, the two female protagonists are 'thrown into a hair-raising world where the horses have cocaine habits and the locals have developed their own alternative to Viagra'.
Bee was described as 'blonde, twenty-three years, 34-22-32 inches' and 'not the type of girl to get dumped'. It adds: 'Ever since she was old enough to understand the rules of kiss-chase she's been besieged by men frantically reciting their best comic material at her in the hope that she'll stay still and in view for just a little while longer.
'These boys have a point. Bee's charms don't stop at her face and figure. She's extremely good company and blessed with an almost French capacity for pouty sulking.'
The book goes into some of the dilemmas faced by the girls when hunting. 'Should we wear big sports knickers for comfort? Or skimpy lace G-strings in the hope that Ledbury lives up to its Jilly Cooperesque reputation for lust in the saddle? Then there is the Visible Panty Line conundrum to consider.' Molly said the idea for the book came after historian Niall Ferguson suggested she should write a 'Bridget Jones goes hunting' story. Philosopher Roger Scruton described it as 'stylish and compelling' while journalist Toby Young praised Molly as 'our generation's Nancy Mitford'.
Eventually, however, Molly and Bee's exciting life in the countryside became more mundane. Molly has worked as a business consultant since 2007, while Bee began a career in politics as a research assistant for Lord Strathclyde, then Tory leader in the Lords.
In September 2004, three members of the Ledbury set invaded the House of Commons to protest at the Government's ban on hunting.
Cleo Watson has quickly emerged as a vital powerbroker in No 10. Elegant and unflappable, she is one of only a handful of aides who have won the trust of Mr Johnson's dishevelled policy guru Dominic Cummings
They included John Holliday, who was fictionalised in Molly's book as Jack Nightingale, an expert rider with a 'fearless appetite' for women. Bee was suspected – though furiously denied – helping the interlopers gain access. Five years later she married Old Etonian James Roycroft, the founding partner of a London investment firm, who she met at Oxford, which he had represented in the 1997 Boat Race.
Bee worked for Mrs May for four years and had been expected to follow her into Government when the Tory-led coalition was formed in 2010. However, there were rumours her appointment as a special adviser in the Home Office was blocked by Andy Coulson, David Cameron's then Director of Communications. Bee may, therefore, have had mixed emotions as she watched her younger sister Cleo, who had worked on the Vote Leave campaign during the 2016 EU referendum, land a top job in the policy unit in No 10 during Mrs May's premiership.
Cleo remained at the heart of Government after Mr Johnson entered Downing Street and now boasts the title of 'Head of the Prime Minister's Priorities and Campaigns'. She runs a special taskforce that will fast-track new Northern female Tory MPs from the 2019 intake into Government roles.
Crucially, she has formed a strong working relationship with Dominic Cummings, with one Whitehall source describing her as 'the Cummings whisperer' because she is one of very few people in No 10 who can calm down the PM's volatile adviser when he flies into a rage.
Her headmistress, Dr Despontin, is unsurprised by her success. When she saw earlier this month that Cummings had posted a job advert for 'an unusual set of people' to work in No 10, she instantly thought of her former star pupil. 'She was very much an original thinker – a bright, bright girl. I'm not at all surprised that she works so closely with him.'
Despite the achievements in Westminster of Cleo and Bee, it was Nell who shone brightest at school. Dr Despontin recalled how she was head girl and won the headmistress's prize for public speaking.
In 2012 she married Richard Corbet, a land agent and chartered accountant. At the wedding the couple were pictured on a hill overlooking the coast with Nell's parents and her four sisters, including Flora who runs a design business.
Parents Robin and Liza are believed to have moved to Pembrokeshire in recent years, delegating the management of the language school to Bee and their youngest child and only son Archie, 29, who was described by Molly in her book as 'the treasured tsarevich'. They also market the mansion as a wedding venue, B&B and yoga retreat.
Last night, Robin Watson said: 'I am very proud of my daughters, and, of course, my son too. They are all very good friends, which is wonderful.'
While most of the Watson sisters now return to the family home less frequently, they still get together each year at Christmas.
'They are wonderful. They come to our evening service on Christmas Eve pretty much every year,' said Vanessa Westgath, a warden at the lakeside St Gastyn's Church in nearby Llangasty Talyllyn. 'They are always so nice, very pleasant people, and full of energy.'
Additional reporting: Nic North