Reyaad Khan, the boy from Cardiff who joined Isis, was killed by an RAF drone because he had been planning an attack to kill the Queen on VJ Day in London, it is being claimed. Khan, 21, who used the nom de guerreAbu Dujana on Twitter, was one of two militants killed on 21 August. The other militant, Ruhul Amin, 26, was killed with him. A third Briton, Junaid Hussain, 21, was killed by an American drone on 24 August.

Security services foiled a plot to use Improvised Explosive Devices (IEDs) to attempt to cause carnage at the JY event in London on 15 August, the week before Rayeed Khan and Ruhul Amin were killed. Although he didn't directly link Khan to the plot, Cameron said he had been planning "to attack high profile public commemorations."

In the House of Commons, Prime Minister David Cameron defended his decision to authorise the deadly strikes on Syrian soil without prior authorisation from the House. "We were exercising the UK's inherent right to self-defence," he said.

jihadi Junaid Hussain
British computer hacker-turned jihadi Junaid Hussain was killed by an American drone on 24 August Twitter

"There was clear evidence of the individuals in question planning and directing armed attacks against the UK. These were part of a series of actual and foiled attempts to attack the UK and our allies. And in the prevailing circumstances in Syria, the airstrike was the only feasible means of effectively disrupting the attacks planned and directed by this individual."

However acting Labour leader Harriet Harman demanded that the legal advice justifying the strikes be published. "Why didn't the Attorney General authorise this specific action rather than merely 'confirming there was a legal basis for it'?'" asked Harman.

"What was it about this individual and his actions that singled him out from all that has gone before? Did he represent an ongoing threat or was the threat based on a specific act he was plotting?"

Although Cameron insisted the hit was legal, former Attorney General Dominic Grieve suggested the family of Khan might now attempt to sue the government. Grieve told the BBC: "I very strongly suspect that in view of the fact that this man was a British national with family in this country it will probably lead to a legal challenge in due course."