Footage has been released for the first time of the moment an RAF Waddington controlled air strike was conducted on Islamic State fighters before they carried out a public execution.
The video, released by the Ministry of Defence, shows crowds of civilians being forced at gunpoint at gather in the Levant-held town of Abu Kamal in eastern Syrian to watch an execution of two prisoners.
A single Hellfire missile was controlled from 2,000 miles away, manned by servicemen at RAF Waddington near Lincoln using unmanned Reaper drones back in May.
The release came as Defence Secretary Sir Michael Fallon announced that drone pilots who bomb Isil fighters could be awarded military medals.
Footage shows the strike hitting an Isis sniper on a nearby roof. Civilians and fighters scattered before the public killing could be carried out.
The drones have been deployed against Isis since the end of 2014 after Parliament authorised military action.
The mission was overseen from an air operations centre at the al-Udeid air base in Qatar.
The MOD also released the first footage from inside the Qatar military HQ of UK personnel in action.
It said it could not target jihadis on the ground as civilians would have been caught up in the blast.
Air Commodore Johnny Stringer, commander of UK air operations in Iraq and Syria, said: “The individual whom we engaged was a sniper in over-watch to shoot civilians who sought to move away from the execution, let alone to protect the planned execution itself.
“That particular example for us very much brought it home because civilians had been herded in, forced literally at gunpoint, to go and watch this going on in their hundreds.”
He revealed that the UK had taken out Britons in secret missions to stop specific attacks, adding: “By dint of their activity, by being members of Daesh (Isil) and frankly engaging the people we are here to protect, they (British citizens) become valid military targets and that’s the way we look at it.