Prince Charles spoke with London’s Metropolitan Police during their official investigation into the death of Diana, Princess of Wales, according to a new report.

The official police inquiry, known as Operation Paget, began in 2004 and was tasked with investigating the cause of Princess Diana’s death. That included examining the conspiracy theories that her death was in fact a murder carried out by British intelligence agency MI6 at the Royal Family’s behest. The inquiry wrapped in 2008, and a jury found Diana’s death was an “unlawful killing” caused by the drunk driver of Diana’s car, Henri Paul, and the pursuing paparazzi that chased the princess into a Paris tunnel in August 1997.

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However, in following all the leads presented to them by the evidence in their possession, investigators Lord Stevens and DCS Dave Douglas carried out a secret interview with Prince Charles in 2005 over a note Diana wrote to her butler Paul Burrell claiming the Prince of Wales wanted her dead.

“This particular phase in my life is the most dangerous,” Diana wrote in October of 1995, just one month before her fateful interview with BBC journalist Martin Bashir on “Panorama.” “My husband is planning an accident in my car. Brake failure and serious head injury in order to make the path clear for him to marry Tiggy.” Tiggy, aka Tiggy Legge-Bourke, was her sons’ former nanny and a woman Diana believed to be having an affair with Charles.

The princess added, “Camilla is nothing but a decoy so we are being used by the man in every sense of the word.”

In a new interview with the Daily Mail, Lord Stevens recalls the details of how the discovery of this note led to the interview with the future King.

“The interview [with Charles] was unique. Of course it was a unique situation,” Stevens says. “But we approached it as we would any other witness.”

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The conversation was arranged in secret with only Charles, his private secretary, Sir Michael Peat, Stevens and DCS Douglas knowing it was to take place.

Carried out at St. James’ Palace in December 2005, just eight months after Charles wed Camilla (now the Duchess of Cornwall), the interview did little to shed any light on what might have influenced Diana to think Charles was plotting to kill her.

Lord Stevens recalls Prince Charles greeted him with smiles and a friendly hello. “It’s nice to see you again, Lord Stevens,” the prince said before addressing Douglas to ask, “How is the inquiry going? What is it you want us to do today?”

After some polite conversation, Stevens turned to the subject of Diana’s note to Burrell which he then read aloud for the prince.

“Why do you think the Princess wrote this note, Sir?” Stevens asked.

“I did not know anything about [the note] until it was published in the media,” Charles replied.

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Making sure there was no ambiguity over the facts, Stevens followed up: “[So], you didn’t discuss this note with her, Sir?” Charles repeated that he “did not know it existed.”

When asked if he knew “why the Princess had these feelings”, Charles said only, “No, I don’t.”

After concluding the interview with the question all investigators ask interviewees — “is there anything else you would like to tell me, Sir?” — Charles told Stevens and Douglas, “Nothing else, thank you.”

A transcript of the interview was taken down by Douglas and now exists in the National Archives in London. It will eventually be available to the public in 2038.

Crucially, Stevens says neither he nor anyone on the Paget investigation knew about Martin Bashir’s role in feeding Diana’s suspicions and worst fears at the time she wrote her note.

“If there’d been an allegation then that Bashir had produced allegedly fake documents to Princess Diana, which is a criminal offence, we’d have investigated it,” Stevens says. “My goodness me, we would have done.”

“But this [aspect] has only come out recently, which is unfortunate,” he adds. “If we’d known at the time of Paget we would certainly have gone and seen him and interviewed him. And it would have been part and parcel of the inquiry to get to the bottom of it.”