The three days Diana decided her royal marriage was over — has the new movie got it wrong?

Prince Charles And Princess Diana On Their Last Official Trip Together - A Visit To The Republic Of Korea (south Korea). Photo / Getty Images

A new film centered on Princess Diana is already causing quite a stir, and it's not even out yet.

First, there was the controversy surrounding the casting of Kristen Stewart to play Lady Diana.

Now, according to the Daily Mail, new controversy centres on the timeline chosen for the movie plot.

According to the director, Pablo Larrain, the film is a fairy tale in reverse.

"Usually the prince comes and finds the princess, invites her to become his wife and eventually she becomes queen," Larrain said.

"When someone decides not to be queen and says: 'I'd rather go and be myself, it's a big, big decision, a fairy tale upside down."

The plot takes place over just three days, during Christmas at Sandringham.

According to Larrain, it is based on the critical weekend when Diana decided her marriage was over.

Now, critics are wondering whether the director has focused on the right timeline.

Larrain has said the movie takes place in the early 1990s at Sandringham because she "spent so many Christmases there".

However, according to Richard Kay in the Daily Mail, for the first half of Charles and Diana's marriage, they spent Christmas at Windsor Castle and only moved the celebration to Sandringham in the late 1980s.

Charles and Diana. Photo / Getty Images

Larrain has said in interviews the date is "not specific" but has also suggested Christmas 1992.

The problem is that is the one year Diana was not at Sandringham for Christmas at all.

In fact, by then, her marriage was over.

Diana and Charles had formally parted just over two weeks earlier.

She spent Christmas 1992 with her brother Earl Spencer and his family in Northamptonshire.

The movie timeline, with all its artistic licence, would suggest Diana came to the conclusion her marriage was over during those three days in Sandringham.

Writing for the Daily Mail, Kay says it "seems crazy not to stick to the narrative" for this movie, given the Diana saga "is so rich with possibilities and so many twists and turns".

"Surely the lessons of the success of the Netflix hit The Crown are clear: embellish by all means but remain close to the arc of the story, the one the public knows," Kay wrote.

He also suggests the director could have chosen to set the movie three years earlier, in 1989, a significant moment in the real story, when Diana was recorded in conversation with James Gilbey detailing her despair at her marriage.

The conversation with Gilbey is said to have taken place at Sandringham over New Year.

Diana's former Scotland Yard bodyguard Ken Wharfe is convinced 1989 was the year the Princess considered her marriage to be over, despite Diana waiting a few more years to officially end it.

Several months earlier, he witnessed a confrontation between Diana and Camilla Parker Bowles at Camilla's sister's birthday party.

According to the former bodyguard, Diana decided to confront Camilla at the party.

Diana reportedly admitted later that was the moment she realised her marriage was over.

However, once again, she decided to stay, for her boys William and Harry.

There's also the time in 1987 when Diana and Charles were no longer sharing a bedroom and she became involved with James Hewitt.

Or, years earlier even, when in 1982, pregnant with Prince William, Diana threw herself down the staircase at Sandringham, landing at the feet of the Queen Mother.

We could also look beyond the movie's timeline, to November 1992, the last weekend Diana ever spent at Highgrove, and when she was absent from Princess Anne's wedding, despite assurances from the Queen she would continue to attend family occasions.

Whatever episode is chosen to illustrate the end of Diana and Charles' marriage, one conclusion remains the same: she emerges from it, not the shy girl who married a Prince, but the strong woman who got out of the life that was anything but a fairytale.