By Hannah O’Grady and Joel Gunter
BBC Panorama

SAS operatives in Afghanistan repeatedly killed detainees and unarmed men in suspicious circumstances, according to a BBC investigation.

Newly obtained military reports suggest that one unit may have unlawfully killed 54 people in one six-month tour.

The BBC found evidence suggesting the former head of special forces failed to pass on evidence to a murder inquiry.

The Ministry of Defence said British troops “served with courage and professionalism in Afghanistan”.

The BBC understands that General Sir Mark Carleton-Smith, the former head of UK Special Forces, was briefed about the alleged unlawful killings but did not pass on the evidence to the Royal Military Police, even after the RMP began a murder investigation into the SAS squadron.

General Carleton-Smith, who went on to become head of the Army before stepping down last month, declined to comment for this story.

BBC Panorama analysed hundreds of pages of SAS operational accounts, including reports covering more than a dozen “kill or capture” raids carried out by one SAS squadron in Helmand in 2010/11.

Individuals who served with the SAS squadron on that deployment told the BBC they witnessed the SAS operatives kill unarmed people during night raids.

They also said they saw the operatives using so-called “drop weapons” – AK-47s planted at a scene to justify the killing of an unarmed person.