But 21 years after her death, the fact that Diana's life ended so suddenly is still as tragic as ever, although it was only one of the many sliding doors that came to define her.

From her marriage to Prince Charles, the relationship with Dodi Fayed and the decision to go on holiday with her new lover, here is how Diana's fate was sealed in a handful of decisions of a fraction of a second.

Diana's last vacation

The fatal journey of the princess with Dodi Fayed was a last-minute decision from a lonely Diana who had been stranded in London without friends or family.

The humanitarian princess had returned to Kensington Palace after a trip to Bosnia with her charity on landmines, just as Prince Charles brought his sons Prince William and Prince Harry to Balmoral.

& # 39; I'm sure she missed the boys. She was at a loss in London, "royal biographer and author of Diana: the intimate portrait Judy Wade told People.

"Diana had alienated most friends with whom she was on holiday at that time of the year. & # 39;

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In a spur of the moment and an isolated feeling, the Princess decided to accept an invitation to Mediterranean holidays from Dodi Fayed, a notorious playboy and the 42-year-old son of the Egyptian affairs Mohamed Al Fayed.

Diana had met Dodi only a month ago while staying in Mohamed's villa in St. Tropez with William and Harry.

Their relationship was a rebound for Diana, with the princess reportedly still heartbroken about her two-year relationship with Pakistani surgeon Hasnat Khan ending abruptly earlier that year.

Flying to the Mediterranean Sea to relax on Dodi's hunt, Diana and her new lover enjoyed nine days of relative anonymity before the paparazzi caught up with them in Sardinia.

Heard by photographers, Dodi and Diana made a fateful decision there; the couple would leave the island early for a night in Paris before returning to London.

But when they arrived in the city of love, the paparazzi were just as ruthless, so they fled the Ritz hotel where they stayed in the middle of the night.

Only three minutes later, the Mercedes with which she drove collided with a concrete pillar in the Pont de l'Alma tunnel, where Dodi was immediately killed while Diana died four hours later in the hospital.

Tests would later show that the driver of the car, Ritz Hotel security officer Henri Paul, had reached the legal limit three times.

How Diana almost did not marry Charles – twice

Although the engagement of Diana Spencer with the Prince of Wales was a matter carefully directed by the palace, their marriage was only possible thanks to two decisions that had been dealt with by different people for almost a decade.

Years before Diana was ever in the picture, a 24-year-old Prince Charles was quietly dating the socialist Camilla Shand – better known as Camilla Parker Bowles and his future second wife, the Duchess of Cornwall.

According to the biography of Sally Bedell Smith Prince Charles, the heir to the throne hesitated to introduce his girlfriend, worried about their young age and the fact that Camilla did not seem "virgin."

Left over their relationship, Charles went to the Caribbean with the Navy in January 1973 and Camilla reconnected with an old friend, Andrew Parker Bowles.

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It was then, according to Bedell Smith, that Camilla's father and brother came in to make sure that she would not marry Charles, thus changing history in the process.

"They have intervened by publishing an order confirmation in The times on 15 March. His hand was publicly forced and Andrew introduced his girlfriend for almost seven years, "wrote Bedell Smith.

When Charles heard the engagement days later, he was devastated, unable to understand how "such a blissful, peaceful and mutually happy relationship" had ended so suddenly.

Fast-forward eight years later until 1981 when a 19-year-old Diana was only a few weeks away from marrying Charles.

Her happiness was abruptly stopped when she discovered that her fiancée friend Camilla was more than just a friend and was actually his mistress.

In documentary Diana: In Her Own Words, audio interviews the princess gave biographer Andrew Morton reveal how an earlier attempt to confront Charles about a bracelet that he gave Camilla nowhere on.

"(Charles) absolutely cut me dead, it was as if he had made his decision and if it did not work, it would not work," she said.

Unhappy and torn if she would still marry Charles, Diana had one last chance to break her engagement.

The moment came when Camilla interrupted the last meeting of Diana with Charles before he went on a trip.

But instead of confronting him, Diana made the decision not to say something, which sealed her fate in the process.

"I was talking to him about his trip in his study." The telephone rang, it was Camilla, just before he went five weeks, "Diana said.

"So I thought:" Will I be nice or will I just sit here? "So I thought I would be nice, so I left them and it just broke my heart."