Diana never publicly acknowledged her love for Hoare as she did for Cavalry officer James Hewitt. Picture: AFP

London - Of all the men drawn into the vortex of Princess Diana’s life, he was one of the few to emerge with any credit. He was also the unlikeliest of suitors - a close friend of Prince Charles.

Too well-bred to ever allow his emotions to go on public display, Oliver Hoare weathered the endless speculation about his affair with the Princess of Wales with a wearied insouciance, keeping both his dignity and his silence.

Diana never publicly acknowledged her love for Hoare as she did for Cavalry officer James Hewitt, or allowed her friends to talk of him as they did subsequently of other men friends such as Hasnat Khan or Dodi Fayed.

But then her relationship with the married art dealer was by some distance the most dangerous, the most destabilising and the most humiliating of her life. It was also the most passionate.

Almost 25 years have passed since revelations about the couple exploded into the public consciousness after Diana was accused of bombarding the Hoare family home with more than 300 nuisance telephone calls.

Yet, throughout that near quarter of a century, Hoare said nothing. Now with his death at 73, after confronting illness with both bravery and dark humour, the Old Etonian has ensured what he always vowed — that he would take the secrets of the affair to his grave — has come to pass.

Diana’s infatuation with the dashing father-of-three was so intense, so all-consuming that for a brief moment she considered leaving Charles for him.

Indeed, he was the only man she truly ever thought of giving up everything for. At the height of her unhappiness with Charles, the address where Hoare lived in Chelsea, Tregunter Road, was the code word she and her sister-in-law the Duchess of York devised to describe their clandestine plans to abandon their husbands and their royal lives.

"Tregunter Road was our code for escape," she once told me, "it meant our leap for freedom." By then, however, her love for Hoare had subsided, but her wish for a life outside the Royal Family had not.

It has always been said that Diana lost her nerve for that double break-out with Fergie from behind palace walls. And that when Fergie’s split from Prince Andrew was announced, the princess - whose marital unhappiness was the greater of the two women - quietly changed her mind.

That, though, was only half the story. Many believed that if push had come to shove, Hoare himself would anyway not have walked out on his own family. He once ruefully quipped that however rich he could possibly become, he would "never be rich enough to look after a princess".

It was also significant that while Diana’s domestic life was joyless, his was happy, if chaotic. His French-born wife Diane had displayed great reserves of emotional resilience to steer her family through the crisis wrought by the princess’s unquenchable ardour for her husband.

Hoare’s continuing devotion to Diane and for his daughter and two sons were also key factors.

And unlike others over whom Diana cast a shadow, Oliver handled it so much better - and infinitely more stylishly.

Remarkably, he remained a friend of the Prince of Wales, who for many years spent part of each summer at the Hoares’ French retreat in rural Provence, sometimes with Camilla. He had also been one of the few insiders who had known about the prince’s relationship with the former Mrs Parker Bowles.