The Metropolitan Police has said there is "no credible evidence" the SAS was involved in the death of Diana, Princess of Wales.
In a letter obtained by Sky News, Assistant Commissioner Mark Rowley said: "Whilst there is a possibility that the alleged comments in relation to the SAS's involvement in the death may have been made, there is no credible or relevant evidence to support a theory that such claims had any basis in fact.
"Having reviewed the exercise and its findings, I am satisfied that there is no evidential basis upon which therefore to re-open any criminal homicide investigation or refer the matter back to the coroner.
"In light of this information, I have today also written to the Royal House and Lord Justice Baker informing them of the above and providing a copy of the concluding summary."
The investigation began after police received information in August that alleged members or former members of the Special Air Service (SAS) were involved in circumstances leading to the deaths of Diana, Dodi al Fayed and their chauffeur Henri Paul on August 31, 1997.
As a result of the information police commenced a "scoping" exercise to assess the credibility of the allegations.
For three months a team of seven detectives investigated the claims and liaised with West Mercia, Dyfed Powys and West Midlands Police as well as with the Royal Military Police and the Ministry of Defence.
Officers were also given access to Special Forces Directorate records.
The police concluding summary says there are contradictions as to whether individuals did or did not make claims that people associated with the SAS had some involvement in the deaths.
The summary said: "It is not possible to prove conclusively what was, or was not said.
"It is, however, very clear that in the extraordinary publicity and conjecture that followed the deaths and the inquests, there will have been those who, for whatever motivation, will have sought to demonstrate particular inside knowledge, or to claim some form of kudos or recognition."
An inquest in 2008 into the deaths lasted more than 90 days and heard from about 250 witnesses.
It returned a verdict of unlawful killing and grossly negligent driving of the Mercedes and of the vehicles following when it crashed in a Paris tunnel after leaving the Ritz hotel.
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