In The Crown season 5, Diana's inner circle is small, with the Princess of Wales largely cutting a lonely figure.
But there are a handful of individuals that she confides in long before her eye-opening interviews with Andrew Morton and Martin Bashir - one of who is James Colthurst.
After meeting Diana in 1979, he became her confidante. But what was their relationship like and who plays him in The Crown's latest instalment?
Who was James Colthurst?
James Colthurst was born in Cork, Ireland and comes from privileged stock. His brother is Sir Charles St John Colthurst, Baronet, the owner of Blarney Castle.
He attended Eton college before going on to study medicine and becoming a radiologist. He completed his training at St James's University Hospital in London.
It was his medical background which led to his first meeting with Diana, according to a 2021 article in The Telegraph.
17-year-old Diana met Colthurst on a ski holiday in Val Claret back in 1979, shortly before her marriage to Charles in 1981. She was working as a nanny at the time.
"She knew several of the friends I was with, and they brought her back to our apartment when she twisted her ankle, telling her I would look at it," he said.
Colthurst described her as "good fun, bright and mischievous" and said "it was hard not to hit it off with Diana straight away".
In ITV documentary Diana, Colthurst recalled a prank he pulled on her, sticking L plates on her car and tying a string of tin cans underneath. She responded by chucking eggs and flour at his car.
It was Colthurst who introduced Diana to Morton, who wrote Diana: Her True Story - In Her Own Words. According to Vanity Fair, the doctor invited the Princess to attend St Thomas's in 1986. Morton was present on the day, alongside other press, and he formed a friendship with Colthurst, the pair meeting regularly to play squash.
"We never talked about Diana," said Morton. "He is a polymath with a lot of great ideas. He is fascinating company."
It was Colthurst who delivered the tapes containing Diana's innermost thoughts to Morton.
"The tape visits were lunch," he told 60 Minutes. "I'd cycle in, the recorder was in the briefcase - nothing surprising there - I'd go in and we'd normally sit down and have a few questions [from Morton] before lunch. After lunch and during coffee I'd clip the microphone on again and she'd finish them off.
"She was enormously enthusiastic to have her story out there, she knew exactly what she was doing."
In Channel 4 documentary Diana: In Her Own Words, Colthurst also said the royal feared she would "lose" her children if she didn't publicly defend herself.
According to Colthurst, Diana was concerned that her friend would be "deliberately knocked off" his bike by those looking to prevent the publication of Morton's book.
"She voiced this fear several times to me," he said. "It might sound like paranoia, but I don't think she was paranoid."
When his mother Lady Colthurst was asked about his involvement in the writing of Morton's book, she said (via The Times): "All we have learnt about the situation we have read in the papers."
Her mother-in-law Janet also echoed that: "We know absolutely nothing about this business, so there is nothing to say."
Colthurst also said (via The Telegraph) that he helped Diana write a number of public addresses due to her "prodigious set of engagements", adding: "Perhaps one of the toughest features of being her friend was trying to encourage her to limit her task list as well as coaxing her over the many bumpy moments which she found almost overwhelming."
Colthurst also said the day before Diana was photographed hugging an AIDS patient, the pair had had a discussion about HIV transmissibility, with Colthurst informing her that "shaking hands and so on was safe".
Naturally, Diana and Colthurst also discussed her relationship with Charles. He alleges that there was "jealousy" from Charles's team due to Diana's "growing profile", which is tackled in season 4 of The Crown during the couple's trip to Australia.
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"I felt, when she joined the royal family, she may not have been fully aware of the machine she was in," he added. "The Firm, for its part, was unaccustomed to having a superstar in its midst, and I don't think it knew how to cope with the enormous amount of publicity she generated."
Colthurst said that during the most challenging years of her marriage, he would "sometimes receive between eight and 10 calls from her a day".
Who plays James Colthurst in The Crown?
James Colthurst is played by stage and screen actor Oliver Chris.
Recently, he has appeared in BBC drama A Very British Scandal as George Emslie QC, who represented the Duke of Argyll (Paul Bettany).
He also plays Jason's best friend Freddy in Apple TV+ series Trying, and Julia's disinterested husband Paul in Motherland.
You might also recognise him from BBC Three sitcom Bluestone 42, ITV drama Breathless, ITV comedy series Bonkers, Channel 4 sitcom Green Wing and BBC romantic comedy Rescue Me.
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