SAS wife's bombshell: Regiment bribed me to keep silent about Diana murder claims Incredible story of key witness that has a terrifying ring of truth SAS officer 'warned her that she would end up dead like Lee Rigby' She has now gone into hiding claiming she fears for her own safety Sniper husband claimed that the SAS was "behind" Princess Diana's death By Mark Nicol Defence Correspondent The former wife of an SAS sniper has sensationally claimed that she was paid cash to buy her silence about his astonishing accusation that Princess Diana was murdered by the elite regiment. The woman, who cannot be named for legal reasons but who we will call Sarah, says she was given a brown envelope stuffed with bank notes by an SAS officer who told her to "keep quiet about Diana." The sniper's claim that the SAS was "behind" Princess Diana's death emerged last year at the court martial of Sergeant Danny Nightingale, who was found guilty of illegally possessing a handgun and ammunition. In hiding: The ex-wife of Soldier N says she now fears for her own safety after claiming to have been threatened by an SAS officer Yesterday, speaking for the first time about her "nightmare" marriage to the sniper known as Soldier N - who made the claim - 40-year-old Sarah revealed that: Scotland Yard detectives who probed the alleged SAS link to Princess Diana's death are themselves now under scrutiny by the Metropolitan Police's Serious Misconduct Investigation Unit over claims that they intercepted an email sent by the wife of Soldier N. An SAS officer warned her that she would "end up dead like the Woolwich soldier" Lee Rigby if she gave evidence that undermined her former husband's witness testimony at Nightingale's court martial. She told SAS top brass in 2010 that her husband was unstable and should not deploy to Afghanistan the following year. Soldier N was later found guilty of illegally possessing a high-powered pistol, a silencer, hundreds of rounds of ammunition and a hand grenade. Sarah, who is in hiding as she now fears for her own safety, said: "The threatening and sinister way that the SAS dealt with me made what my husband had said about the regiment's role in Diana's death all the more believable. I had never been handed £500 before and told to keep quiet about the payment and what it was for. They wanted me to keep quiet about Diana and SAS operations. But I couldn't stay silent about something so serious. The payment was deeply suspicious and made me very uncomfortable. Soldier N's claim that the SAS killed Princess Diana was made in a letter written by the woman's mother to the regiment's Commanding Officer (CO) in September 2011. Sergeant Danny Nightingale with his wife Sally Sarah says that weeks later she was visited at her marital home by an SAS officer. Soon after that, she had another meeting with a representative from a Services" charity and two SAS officers who told her they were visiting her on behalf of the Commanding Officer. At this meeting Sarah says the SAS officers repeatedly denied another claim made by Soldier N - also detailed in the letter sent to the SAS Commanding Officer - that troops from the elite regiment would encourage each other with rewards to harass or harm individuals who were causing them difficulties. The soldiers would apparently write the person's name, address and details on a slip of paper and place this in a box along with a cash payment. Another meeting between the SAS officer and Sarah took place in early 2012 when, she says, the officer handed over a brown envelope containing £500 and insisted that she should never discuss the payment with anyone, or discuss the Diana claim with anyone. Sarah said last night: "The strange thing was that at no time during this meeting did the officers mention what my ex-husband had said about the SAS being involved in Princess Diana's death." Indeed, the contents of the letter only became public knowledge last year following Sgt Nightingale's second court martial for possessing the gun and ammunition, when Soldier N appeared as a prosecution witness for the Army against Sgt Nightingale. Sarah said: "The fact that they stayed silent about Diana compounded my belief that my ex-husband had told me the truth in 2008 when he talked about an SAS soldier directing a beam of light into the eyes of Princess Diana's chauffeur as their Mercedes entered the Pont d'Alma road tunnel. My husband had added that after the SAS had caused the car to crash, a soldier had run back to the wreckage and looked inside to see how badly Princess Diana was hurt. Apparently he then gave a signal to a colleague that their mission had been successful. So now I'm convinced that this operation is the SAS's big secret. Front line: Soldier N pictured in the desert next to an SAS Land Rover during the Iraq War in 2003 Yet another meeting with the SAS took place in June last year, and it left Sarah terrified. She says that at that meeting the SAS officer suggested that she could "end up dead like the Woolwich soldier" Lee Rigby if she spoke out against the regiment. At the time she was separated from Soldier N and was struggling to pay her household bills. The officer collected the payment notices and promised her that he would take care of them for her. But just as he was leaving Sarah's house the conversation apparently took a dark turn and she was asked whether she was going to give evidence against the Army in its case against Sgt Nightingale, due to take place the following month. Sarah recalled: "The officer said that if I spoke out in support of Danny, and against my former husband who was the Army's main prosecution witness, I might have cause to worry about my safety and my children's safety. "I was already shocked but he then said that if I went public with anything I knew I could "end up dead like the Woolwich soldier." He was staring at me the whole time he was saying this and he was very intimidating. Last moments: Princess Diana in her doomed car driving through Paris Princess Diana and Dodi Fayed inside the lift at the Ritz Hotel I was really trembling as he left my house. Thankfully I had arranged for Theresa Lumby from the charity Women's Aid to be present. She heard what the officer was saying to me and gave a statement to Danny Nightingale's solicitor, Simon McKay. Ms Lumby declined to comment on the incident last night, but Mr McKay said: "Theresa Lumby overheard a conversation between the officer from the SAS and the former wife of Soldier N which touched on the fate of the Woolwich soldier Lee Rigby. The impression of Theresa and the former wife was that this comment and others made by the officer about potential threats were intended to dissuade her from giving evidence on behalf of Sergeant Nightingale at his second court martial. The incident was reported to the Service Prosecuting Authority as the defence was concerned it may amount to an attempt to intimidate a witness. Landmark: The SAS clock tower in Hereford the regiment's home town Mr McKay added: "This is a matter of deep concern. The Metropolitan Police's standards unit has now launched an investigation. Even though two inquiries - by Scotland Yard and the French police - had found Princess Diana's death was an accident, the claim included in Sarah's mother's letter led to the Metropolitan Police to reopen Operation Paget, the official UK investigation into the fatal accident in Paris on August 31, 1997. This led to yet another bizarre twist in the tale. As part of the new inquiry, on August 28 last year Sarah and her mother attended a police station in West Wales where they were interviewed by two senior detectives. At this meeting the officers handed her a copy of an email she had sent to her lawyer detailing her husband's "erratic" behaviour during their marriage. The 17-page document also briefly mentioned Soldier N's claim that the SAS had assassinated Princess Diana. Sarah said last night: "When I saw the statement I was shocked because I knew that I had not sent the email to anyone other than my divorce lawyer. Later I confirmed with her that she had not sent the email to any third party. So I am sure that the police intercepted this email. Scotland Yard's Serious Misconduct Investigation Unit is now investigating how their officers came to have a copy of the email. A Scotland Yard spokesman said: "We are aware of the complaint which is the subject of an ongoing investigation." And an Ministry of Defence spokesman said: "As the Metropolitan Police have said previously, when considering the allegations made in this letter they have found no evidential basis upon which to open any criminal investigation. We take the welfare of our troops and their dependants extremely seriously and it is normal for service personnel and their families to be briefed on personal security measures, especially so at a time when they are likely to receive a high level of media attention.