Scotland Yard said it is “scoping” the information and “assessing its relevance and credibility”.
The claims were passed to the Metropolitan Police by the Royal Military Police (RMP), which was told of them by the former parents-in-law of a former soldier based on information that the ex-soldier had talked about, according to a military source.
A letter given to the RMP is said to allege that the SAS was “behind Princess Diana’s death”, according to reports yesterday, and to also refer to the princess’s “secret diary”, in which she allegedly made certain claims.
The letter reportedly claimed the soldier was a special forces member who was a former housemate of Sergeant Danny Nightingale, who was found guilty of illegally possessing a gun and ammunition.
The allegations do not specify how exactly the SAS were involved – but several years ago, a Germany weekly magazine ran an interview alleging that specially trained marksmen shot at the tyres on the car Princess Diana was travelling in as it entered the Paris tunnel in 1997.
Other theories included claims that the black S280 Mercedes had hit a white Fiat Uno car before the crash.
The essence of the allegations made by Dodi’s father, Mohammed Fayed, were that the white Fiat Uno was used by the “security services” to block the road in front of the Mercedes, causing it to swerve and thereby crash into the side of the tunnel.
A statement issued by Scotland Yard yesterday said: “The Metropolitan Police Service is scoping information that has recently been received in relation to the deaths and assessing its relevance and credibility.
“The assessment will be carried out by officers from the specialist crime and operations command. This is not a re-investigation and does not come under Operation Paget.”
Paget investigated conspiracy theories about the fatal August 1997 crash in Paris.
A royal spokeswoman said there would be no comment from the Duke of Cambridge, Prince Harry, or Clarence House.
The princess, Mr Fayed and chauffeur Henri Paul died after their Mercedes crashed in a tunnel after it left the Ritz Hotel on the morning of 31 August.
Diana, mother of William and Harry, was 36 at the time of her death, while Mr Fayed was 42.
The hearing into their deaths lasted more than 90 days with evidence from 250 witnesses.
The inquests, which cost £8 million overall, concluded on 7 April, 2008, with a jury returning a verdict that the princess and her boyfriend were unlawfully killed.
Former Met Police commissioner Lord Stevens’s Paget investigation was launched in 2004 at the request of Michael Burgess, the royal coroner.
The former top policeman published his report in December 2006, rejecting the murder claims voiced by some, including Mr Fayed’s father.
Lord Stevens’s investigation found that Diana was not murdered by British spies nor by the Duke of Edinburgh and she was not pregnant nor engaged to her boyfriend.
Operation Paget concluded, just like the French investigation in 1999, that Mr Paul was drunk and driving at excessive speed.
The Mercedes was being driven through the Pont de l’Alma tunnel in Paris at about 61mph – twice that road’s speed limit.
The Ministry of Defence declined to comment.
A spokesman for Mohammed al-Fayed said he had no comment, but said he will be “interested in seeing the outcome”.
Dickie Arbiter: ‘Some people have nothing better to do’
IT SEEMS to me that these stories appear with monotonous regularity around the time of the anniversary of the death of Diana, Princess of Wales. You have to say to yourself if there was something there, why has it taken 16 years to come out? What we have is a statement from the former in-laws of a former solider. It’s a red herring. It doesn’t make sense.
It’s like the killing of President John F Kennedy, there have been conspiracy theories for 50 years. Now we have the same with Diana. I can only think people have nothing better to do.
The inquest was conclusive. There was a thorough Met investigation. There was a thorough French investigation. It was an accident.
Of course, as soon as there’s something that comes out of Scotland Yard involving Diana, it’s a story. As soon as they have information, they have to pursue it. It would be more of a story if they didn’t. Sixteen years on, Diana is still a story. There are still books being written about her and we even have the actress Naomi Watts, who is playing Diana in a film, making the outrageous comment that she was given permission from Diana from beyond the grave.
This is a story which is always going to have people coming out of the woodwork. If it had been a Mrs Jones who died no more would have been heard. As we have William and Harry, they’re seen as cannon fodder – it’s easy to go to the soft underbelly of the royal family and come out with another story.
• Dickie Arbiter is a royal commentator and the Queen’s former press spokesman.