Back in 2005, Prince Charles was questioned by police about the tragic death of his ex-wife, Princess Diana, according to a new report. The former head of Scotland Yard, John Stevens, who led the investigation into the various conspiracy theories surrounding the fatal car accident, spoke to the Prince of Wales about a note Princess Diana wrote in 1995.

In the note, Diana claimed Charles was planning "an accident" with her car, adding that his goal was "brake failure and serious head injury." At the time the note was written, Diana and Charles were still married. The late princess believed Charles wanted to marry Tiggy Legge-Bourke, a nanny for Prince William and Prince Harry. Charles and Diana would go on to divorce one year later in 1996.

Diana's note was published in the press six years after her passing. Two years later, Prince Charles decided to cooperate with the investigation into his ex-wife's death and submitted to an interview at St. James's Palace.

"Yes, allegations had been made about the Prince of Wales and other royals but we had to find or examine the [existing] evidence before we approached him with formal questions," Stevens told the Daily Mail. "We found no other evidence to support the scenario suggested in Diana's note."

"We were left with the note, which in itself was not enough to make Charles a formal suspect," he continued. "If he chose to assist [Operation] Paget, he would be doing so voluntarily as a potential witness. We would not be interviewing him under caution."

During the investigation, the former head of Scotland Yard presented the note to Charles before him: "Why do you think the princess wrote this note, sir?" Charles replied: "I did not know anything about [the note] until it was published in the media."

Stevens asked Charles whether he ever discussed the note with Diana, to which he replied: "No, I did not know it existed." Charles also denied knowing why Diana felt that way at the time. "At the end of the day he was incredibly cooperative because he had nothing to hide," Stevens told the outlet.

Diana reportedly wrote that note around the time of her infamous BBC Panorama interview with Martin Bashir. Just last month, an inquiry confirmed the long-held belief that Bashir used "deceitful methods" to secure his televised interview with the royal by showing her fake bank statements.

Following the inquiry into Bashir's methods, Prince William released a public statement on the matter. He recalled his mother's "paranoia" during that time. "BBC employees lied and used fake documents to obtain the interview with my mother; made lurid and false claims about the Royal Family which played on her fears and fuelled paranoia; displayed woeful incompetence when investigating complaints and concerns about the program, and were evasive in their reporting to the media and covered up what they knew from their internal investigation," he said.

Stevens and Scotland Yard were not aware of Bashir's tactics at the time of the Operation Paget investigation. "If there'd been an allegation then that Bashir had produced allegedly fake documents to Princess Diana, which is a criminal offense, we'd have investigated it. My goodness me, we would have done," Stevens reflected. "But this has only come out recently, which is unfortunate."