Another Briton was killed alongside him, Ruhul Amin, also an Isis member, who happened to be in vehicle with him. Cameron also confirmed that a third Briton had been targeted and killed in a separate drone strike by the US as part of a joint operation three days later. To put this in perspective – to illustrate what a major departure this is – look across the Atlantic at the long-running controversy about drones. The US has been in the forefront of the use of drones with Barack Obama employing even more of them than George W Bush. Americans have been killed, though the US insists these were inadvertent: people who were in the wrong place at the wrong time.

Washington has only admitted to one targeted killing by a drone of an American citizen, Anwar al-Awlaki. The preacher, accused of working with al-Qaida, was hit in a strike by a Hellfire missile in Yemen in 2011. But now the UK has acknowledged that at least two British citizens were targeted for drone strikes.

Chris Cole, the head of the campaign group Drone Wars, said of Khan: "This was the deliberate killing of a British citizen. It is shocking. We have not seen this before."