The Princess Royal’s 63-year-old former husband has left his second wife, Sandy, to set up home with fellow equestrian Lauren Hough, 35.
Sources close to Capt Phillips said he broke the news to his 58-year-old wife and their 14-year-old daughter Stephanie earlier this year.
The couple’s separation and forthcoming divorce were confirmed to The Daily Telegraph in a statement from Capt Phillips’ solicitors at the law firm CKFT.
It said: “Captain and Mrs Mark Phillips are separating and divorce proceedings have commenced. The couple have a daughter, aged 14, and the care and support of her is Capt Phillips’s main concern at this sensitive time.
“Capt Phillips therefore requests that all parties respect their privacy in the months ahead.”
Capt Phillips, an Olympic gold medallist in three-day eventing, grew close to American Miss Hough through his work as trainer of the US eventing team.
He spends several months a year in the US, where he has worked with the national eventing team for 20 years, and when he is in the UK he regularly travels around the country designing eventing courses.
Ironically, he announced two years ago that he would step down as Chef d’Equipe of the US team after the London 2012 Olympics, saying his transatlantic commuting was “not getting any easier”.
But instead of returning home to his farm in Cherington, near Tetbury, Glos., he is understood to be planning to set up home in Florida with Miss Hough.
He has reportedly told friends that “I might only be alive for another five or ten years so I might as well be happy”.
Capt Phillips’ decision to set up home with a younger woman is likely to prompt a certain sense of déjà vu for his current wife.
Both Sandy Phillips and Miss Hough are slim, blonde US Olympians who are younger than their predecessors at Capt Phillips’ side.
Hawaiian-born Sandy Pflueger, as she was then, was part of the US dressage team at the 1984 Los Angeles Olympics and went on to help coach the US team alongside her husband.
Miss Hough was part of the US team at the Sydney Olympics in 2000, and will also be helping coach the US team alongside Capt Phillips at the London 2012 Games.
Sources in the US said Capt Phillips and Miss Hough recently told members of the US eventing team about their relationship to “get it out in the open” after Miss Hough began coaching members of the team in showjumping, one of the three disciplines of eventing.
Since then the couple have been seen holding hands at equestrian events.
Sources close to Miss Hough said she and Capt Phillips began house-hunting after Miss Hough sold her home in Wellington, in Florida’s Palm Beach County, last month.
James Wolf, executive director, sport programs for the US Equestrian Federation, said Miss Hough would “definitely” be at London 2012 as a coach and could “possibly” be competing, though she is unlikely to qualify on current form.
Born in California, Miss Hough is the daughter of another Olympian, Charles “Champ” Hough, who won a bronze medal in team eventing at the Helsinki Games in 1952. Her mother, Linda, ran a hunter and jumper stable for 25 years.
She has won countless trophies during her 20-year career and on her personal website she lists cooking, reading, working out in the gym and “hanging out with her dog, April”, as her hobbies.
During his 19-year-marriage to the Princess Royal, with whom he has two children, Zara and Peter, Capt Phillips fathered another daughter, Felicity, as the result of an affair with Heather Tonkin, an art teacher in New Zealand.
Felicity Tonkin, how an equine vet, was born in 1985 but Capt Phillips was only confirmed as her father in 1991 following a DNA test during a paternity suit.
Capt Phillips met both of his wives through equestrianism. The Princess Royal rode for Britain in the 1976 Olympics in Montreal, four years after Capt Phillips won his gold medal at the 1972 Munich Olympics.
Miss Pflueger married Capt Phillips in 1997, becoming stepmother to Zara Phillips and Peter Phillips. Last year she joined her husband for Zara Phillips’ wedding in Edinburgh, where Capt Phillips gave the bride away.
Sandy Phillips declined to comment and Miss Hough was unavailable.