He is the flame-haired equerry turned pub owner who saw his name resurface in the headlines after the release of Harry’s memoir, Spare.
In the book, he appears as the finger-wagging royal bodyguard who confronted the prince about his use of illegal drugs.
But in reality, Dyer was also a mentor, a big brother figure and even a ‘second dad’ to Harry and William after the death of their mother in 1997.
The former Welsh Guards officer, known as Marko to his friends, would visit William at boarding school, helped foster Harry’s romantic relationships and protected the young prince from prying photographers.
Former Welsh Guards officer Mark Dyer, known as Marko to his friends, worked as an equerry to Charles in the 1990s
He was also a mentor and a ‘second dad’ to a young Harry and William after the death of their mother in 1997. He is pictured with the Princes in 1999
Since then, he created – and then sold – a chain of pubs. And he has fought a battle with stomach cancer, returning home to his family last year after six weeks in hospital.
His son, Jasper, is Prince Harry’s godson, who served as a page boy at Harry and Meghan’s wedding in 2018.
Dyer, educated at Cheltenham College, was steadying influence and a big brother figure to the princes in the mid-Nineties when he spent 18 months working as an equerry to Charles.
The Prince of Wales appointed Dyer to keep an eye on his sons, a male counterpart to royal nanny Tiggy Legge-Bourke.
During the first half term after Diana’s death, Prince Charles was committed to a five day visit to Africa.
Dyer took Harry along and organised a safari in Botswana for him while the Prince carried out engagements.
But Dyer’s role was not always to provide a softer support for the teenaged prince. Royal biographer Penny Junor once described Mark as one of the ‘few people who talks some sense into him’.
In Spare, Harry recounted losing his virginity to an unnamed older woman in a field behind a ‘very busy pub’ at the age of 17.
Prince Harry became close to Mark Dyer, who travelled with the young royal while he was on his gap year
Dyer is a trustee of Harry’s charity Sentebale, which supports orphans and vulnerable children in Lesotho, many of whom are affected by HIV and AIDS
His son, Jasper, is Prince Harry’s godson, who served as a page boy at Harry and Meghan’s wedding in 2018
He was still a student at Eton College in 2001 when Marko paid him a visit, with Harry suspecting he had heard about the one-night stand – which he described as a ‘humiliating’ experience.
But over lunch in a cafeteria in the city centre, Mark – who had a ‘sombre look’ on his face – told the Prince that he had been sent to ‘find out the truth’ about his drug-taking.
King Charles’s press office had been informed that a newspaper had evidence of Harry taking drugs.
When Harry did admit to smoking cannabis as a teenager, it was Marko who escorted him to spend a day at a residential centre for drug users in Peckham, South London, at the insistence of his father.
When his school years ended, Harry’s closeness to Dyer grew as the pair travelled together to Australia, Argentina and Lesotho during Harry’s gap year.
The two months Harry spent in Lesotho, at the invitation of Dyer’s friend, Prince Seeiso, made a lasting impression on the royal when he worked with orphaned children with Aids and met other traumatised youngsters.
Harry served as an usher at Mark Dyer’s wedding to Amanda Kline at St Edmund’s Church at Crickhowell, in Powys, Wales in 2010
Mark had previously enjoyed a brief romance with ex-royal nanny Tiggy Legge-Bourke. They are pictured together in 1999
Dyer pictured with Meghan Markle watching Harry play polo in 2017. It is said he helped facilitate Prince Harry’s romantic relationships
Mark, pictured with Princess Eugenie’s husband, Jack Brooksbank, served as an usher at Harry and Meghan’s wedding in 2018
When he returned to the UK, Harry told Prince Charles he wanted to start a charity and Dyer was the driving force behind its foundation, alongside Harry and Prince Seeiso, according to Penny Junor.
Harry’s charity Sentebale, of which Dyer is a trustee, supports orphans and vulnerable children in Lesotho, many of whom are affected by HIV and AIDS.
He was reportedly fond of the Prince’s former girlfriend Chelsy Davy and sneaked her out to the ranch where Harry was staying in Argentina during his gap year before starting his Army training at Sandhurst.
He continued his mentoring role even after his time as an official employee of the Prince came to an end.
‘Mark Dyer had been invaluable; he had done a superb job in supporting and guiding both Princes through their adolescence and showing them something of the world – also introducing them to Africa,’ Penny Junor wrote in her biography Prince Harry: Brother, Soldier, Son.
‘The press thought he was a bad influence but he did a bloody good job for them. He had huge integrity, and he was around when they needed advice that didn’t come from their father.’
When Harry began wooing Cressida Bonas in 2013, Mark did his bit to ensure the royal romance ran smoothly.
While Harry was in Afghanistan, it was reported that Dyer was among the close circle of friends he entrusted with keeping the romance alive.
Meanwhile, Dyer enjoyed a brief romance with ex-royal nanny Tiggy Legge-Bourke but wed Texan heiress Amanda Kline in 2010.
Prince Harry was an usher at the ceremony at St Edmund’s Church at Crickhowell, in Powys, Wales. Harry later returned the compliment, asking Dyer to be an usher at his own wedding in 2018.
The Sussexes also asked Marko to be Archie’s godfather. And Harry, in turn, is godfather to Jasper Dyer, served as a page boy at his wedding.
In 2009, Dyer founded the management company MDM Bars and Pubs and ran pubs including the Rolling Stones’ favourite The Cross Keys and The Sand’s End, in Fulham, where Harry is said to have conducted his secret courtship with Meghan.
After being successfully treated for stomach cancer last year, Mark Dyer was able to attend the wedding of his niece Alicia Lowes in Monmouthshire
He sold the pubs in 2017 for more than £10million and said he was going to ‘relax’ for a while. Later, he bought the Brook House Pub in Fulham with business partner Eamonn Manson.
Last year, Dyer was successfully treated after a gruelling battle against stomach cancer and was sent home after six weeks in hospital and 14 hours of surgery.
He was spotted at the wedding of his niece, classical soprano Alicia Lowes when she married long-distance rower Alex Simpson in Monmouthshire.
Speaking of the joy of having her uncle at the ceremony, Alicia told Richard Eden: ‘Last year was hell for Mark, but he’s turned the corner and is cancer-free.’
Read more at DailyMail.co.uk