Members of Britain’s Special Air Service (SAS) are alleged to have covered up evidence that they killed unarmed Afghan civilians in cold blood and falsified mission reports in a potential war crimes scandal that the government has tried to keep secret.

The allegations have emerged in a classified multimillion-pound Royal Military Police (RMP) investigation, Operation Northmoor, which has been run from a secure underground bunker in Cornwall for the past year and a half.

Senior military police and defence sources with a detailed knowledge of the investigation have said that evidence gathered of war crimes by the SAS is “credible”. Part of the inquiry is said to have focused on a particular SAS squadron, which has been described as a “rogue” unit.

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