In the wake of Princess Diana’s death in 1997, the late Queen Elizabeth II reportedly told Paul Burrell that there were "forces at work in my country of which even I have no knowledge".

In his new book, The Royal Insider, Burrell claims that he had a private audience with her Majesty, in which she warned him to "be careful".

“We talked of the dreadful day Diana died,” he writes, "and what I witnessed in Paris before the arrival of the Prince of Wales and Diana’s sisters. ‘It must have been awful for you,’ she said.

“I talked of the many people with whom I had spoken and seen, at which point she offered me a stark warning: ‘Do be careful. There are forces at work in my country of which even I have no knowledge.’”

Without elaborating much further, the monarch made it clear that their meeting was over and, Burrell says, he never met with her again.

Burrell explains that in December 1997, he was feeling “alone and vulnerable” in the wake of Princess Diana’s death.

He alleges that Frances Shand Kydd [Princess Diana’s mother] had been visiting Kensington Palace and shredding huge numbers of documents, many of which were, in his view, of huge historical importance.

During their meeting, Burrell told The Queen: “I could not stand by and watch history be erased or the Princess’s world changed. She had fought so hard for the little privacy that she had and I have kept safe the personal items which she entrusted to me and were locked in my filing cabinet in my pantry.”

Doubt had been cast on Burrell’s claims that he had removed a number of Princess Diana’s personal items from Kensington Palace for safe keeping.

In August 2001, he was charged with stealing 315 items from the estate of his late employer Diana, Princess of Wales, including six items from Prince Charles, and 21 items from Prince William.

He wrote to the King, then Prince Charles, protesting his innocence: “I had been entrusted by the Princess to be the caretaker of sensitive items, as well as there being many items which were gifts. I begged for a meeting to straighten out the confusion,” he recalls.

But Charles did not grant him a meeting, a decision that Burrell says was a “missed opportunity.”

However, he adds, after also reaching out to Prince William with no response, he turned in desperation to the Queen.

He claims that Her Majesty spoke disparagingly of Diana’s mother, suggesting that Mrs Shand-Kydd drank too much.

Burrell added that her Majesty spoke with genuine sadness about her daughter-in-law’s death: "It’s all such a dreadful business,” she told him, adding: “Diana was such a complex and complicated person.

"What she did best of all is connect with people. She was at home with people less fortunate, people wanting. She had an affinity with people.”

But the most important part of the meeting, from Burrell’s point of view, was that it appeared to trigger a crucial intervention in his court case.

During his trial at the Old Bailey, in October 2002, the prosecution barrister, William Boyce conceded that Burrell’s meeting with the Queen was proof that he had, as he had been insisting all along, informed the Royal Family of his intention to store some of Diana’s personal effects in his own home.

The barrister told the court: “The prosecution consider that if the defence were to apply for the jury to be discharged… the prosecution could not oppose that application.”

Outside the court, Burrell said: “The Queen has come through for me. I'm thrilled, I'm so thrilled.”