The five soldiers had been mentoring and living with the Afghan police An inquest into the deaths of five British soldiers in an attack by a rogue Afghan policeman in 2009 resumes on Tuesday.
They were shot at an police checkpoint in Nad-e-Ali in Helmand province.
The suspect, named only as Gulbuddin, opened fire with a machine gun from a rooftop before escaping from the scene.
The soldiers were Warrant Officer Class 1 Darren Chant, Sgt Matthew Telford, Guardsman Jimmy Major, Cpl Steven Boote, and Cpl Nicholas Webster-Smith.
They had taken off their body armour and were drinking tea with their Afghan colleagues in the courtyard of the compound after returning from patrol when the incident happened.
Six more British soldiers and two Afghan policemen were wounded in the attack at Checkpoint Blue 25.
The Taliban said it was responsible for the killings, although UK military sources have suggested it is more likely that the incident was a one-off and unconnected to insurgents.
A preliminary hearing in February was told that the taking of opium and cannabis was commonplace amongst the Afghan National Police, including those being mentored by British forces.
Coroner David Ridley said: “There is a culture that smoking of opium or cannabis is, to them, like to us the smoking of cigarettes.”
Although the hearing was told Gulbuddin was a cannabis user, the coroner said there was no evidence the Afghan man was under the influence of drugs at the time of the attack.
The inquest will resume at Wiltshire and Swindon Coroner’s Court in Trowbridge, Wiltshire.
In a Channel 4 Cutting Edge programme, soldiers injured in the attack revealed how they pretended they were dead to escape the gunman.
Guardsman Steve Loader said: “I’ve never been so scared in my life.”
The troops had been mentoring and living with the Afghan police at a compound.
WO Chant, 40, Sgt Telford, 37, and Guardsman Major, 18, were from the Grenadier Guards, and Cpl Boote, 22, and Cpl Webster-Smith, 24, served with the Royal Military Police.
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