HE made a solo appearance at the US Grand Prix last week - with wife Meghan Markle noticeably absent.
Now, royal experts believe this further affirms rumours that Prince Harry, 39, has become a "lonely figure" and that his once close friendship circle has narrowed.
Royal author Phil Dampier told Fabulous: “There’s been a massive cost for Harry marrying Meghan and moving to California.
“Not only has he lost his family, his royal status and military connections, but he’s also lost a lot of friends.
“I get the impression he hasn't got a circle of drinking buddies he can unwind with in Montecito, which has a population of older people, and I’m sure that takes its toll.
“He is dependent on Meghan for his social life and for someone who was used to being one of the lads, as he was in the Army, that must affect his mental health.”
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We have seen Prince Harry accompanying wife Meghan to a Beyonce concert and charity events, and he was invited to the US Grand Prix in Austin, Texas, by the Mercedes and Red Bull teams.
Phil added that during these sightings “Prince Harry always seems to be a lonely figure, or he’s with corporate PR types who advise and manage his business affairs.”
He added: “He doesn’t look happy to me and I think losing some of his friends must be a factor.
“Harry now seems to want to move in celebrity circles and make friends with the rich and famous, whereas before he was on good terms with old chums in all sorts of fields.”
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One of his long-term friends, who had been close to Prince Harry since their days together at Eton, was classmate Tom “Skippy” Inskip.
Phil said: “Tom is apparently out in the cold because he wasn’t sure about Meghan.
“James Corden became a ‘mate’ in California, but he has now moved back to London.
“And while Elton John is always there for him, he mainly lives in Europe.”
There’s been a massive cost for Harry marrying Meghan and moving to California
Phil Dampier
However, some of Prince Harry’s friendships are still active, with Phil adding: “Guy Pelly lives in the States as his wife is American, and he visits him.
“But others he used to play polo with in England no longer communicate with him.
“Of course other relationships have flourished, for example with polo pal Nacho Figueras, who recently accompanied him on a trip to Asia.
“He is full of praise for Harry and they have become close.
“Mark Dyer, a royal aide, still talks to Harry on the phone frequently and he was always a kind of big brother figure or a second dad.
“He is thought to be one of Archie’s godparents and Harry was very concerned recently when Mark fought a cancer battle.”
One relationship that is fragile and appears beyond repair is Harry’s bond with his brother William.
Phil explained: “Of course his best friend, the one person who could really understand him and what he has been through, was his brother William.
Not only has he lost his family, his royal status and military connections, but he’s also lost a lot of friends
Phil Dampier
“Prince William made the fatal mistake of querying whether Meghan was a suitable bride, and if he was rushing into marriage. Their falling out is, quite simply, a Greek tragedy.”
We last saw Harry hobnobbing with Red Bull team boss Christian Horner at the US Grand Prix – donning a black polo shirt and aviator sunglasses in the sweltering Austin heat.
The Duke’s wife Meghan Markle, 42, was noticeably absent from the track after the pair jetted back from a romantic holiday in Caribbean haven Canouan.
The source told: "They looked happy. As Harry walked out of the shop, he slightly bumped into one of the barrels [outside] and they both giggled and Meghan reached for his hand.
"They just looked very happy to be having a holiday together."
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Archie and Lilibet were nowhere to be seen, and it appeared the couple had been away for a kid-free weekend on the resort island.
The island is said to be known as where "billionaires go to escape millionaires" due to its stunning sandy beaches and upscale resorts.