A decade ago, a story appeared in several newspapers about a sad, lonely and emotionally vulnerable woman who had been sectioned under the Mental Health Act. Her name was Dale Tryon, and she warranted little more than a paragraph.

The lady in question was already wheelchair bound, having broken her back falling from a window at a drug and alcohol rehabilitation centre. A few weeks later, she was dead.

Her name will have meant little to most readers.

But a few will have shaken their heads in sadness when they glanced at her name. For this same troubled woman had once come close to winning the heart of a prince.

Her full story is told in Prince Charles’ Other Mistress.

For most people, the battle for Charles’ affections was between two women - Camilla and Diana. But for a time there was another woman in an extraordinary love triangle that existed right up to Charles and Diana’s marriage.

For a period in the 1970s, Dale “Kanga” Tryon and Camilla Parker Bowles were rivals for Charles’s attentions. Both were married to friends of his, both had sons to whom Charles was godfather. We know much about Camilla, but what about Dale Tryon?

Born Dale Harper in 1948 to a wealthy middle-class family in Melbourne, Australia, she suffered spina bifida in childhood. She came to London in the early 1970s and, with her bright and vivacious personality, breezed into London social circles.

In 1973 she married Lord Tryon - one of Prince Charles’ inner circle. It wasn’t long before a strong bond between Dale and the young prince developed.

Biographer Charles Wilson said: “Both women were his mistress. Both bore sons whose godfather he became. Both named them Charles (in Camilla’s case, it was a second name). And, in the end, both hated the other with a loathing that bordered on the pathological.”

Dale was a formidable woman. A great party-goer and giver with a warm and welcoming personality, she became a real favourite amongst the royal family. In turn, she recognised the power she wielded by her close association to the Prince and his family.

She exploited her connections as a successful business woman, creating a popular fashion range; many of her dresses would be worn by Diana herself.

While Dale’s star was in the ascendancy, Camilla was waiting in the wings. Their approach to how they dealt with their positions within the royal circle was the major difference between the two women and would ultimately seal their fates.

Camilla was the consummate insider who knew how to play the royal game, while Dale was a talented amateur who committed the cardinal sin of talking to the Press about her relationships with the Windsors.

As a consequence, she soon found herself excluded.

Years later her mental fragility led to her being sectioned under the Mental Health Act and she died, aged 49, in 1997, only months after Diana.