I've read spy novels, I know how this works.

From the Evening Standard:

British spies are risking their lives daily in Islamic State heartlands to “take the fight to the enemy,” the head of MI6 said today.

Alex Younger stressed agents recruited by the Secret Intelligence Service had penetrated IS “upstream” to stop terror attacks on Britain’s streets.

But in his first public speech, the SIS chief laid bare the perils these individuals faced operating in “the most dangerous and hostile environments on earth” - where paranoid IS fanatics have executed hundreds of people wrongly suspected of being spies.

Spies spend most of their time spying on each other and searching for moles in their own ranks, so it's always good idea to give the other side the impression that you have double agents in their organisations, even if you haven't. Unless you actually have, in which case you have to try and disguise the source of your information etc, in endless twists of logic.

We know that ISIS is just Islamism taken to extremes, they love nothing more than raping, maiming, torturing and killing people and when they run out of victims they just slaughter each other for whatever spurious reason. (The Saudis are hardly better, but for some reason, they count as a reliable ally, go figure). No doubt people in ISIS are paranoid already, of their actual enemies and each other, so basically MI6 has now signed a death warrant for anybody connected with ISIS who has lived in the UK. In which case good work!

If we assume that the head of MI6 is acting rationally, the logical deduction must be that we have no British spies in ISIS. The gamble is, will ISIS assume that Younger is a blithering idiot who has just given away our trade secrets and turn on each other, or will they assume it is a bluff and ignore it? Or is it a double bluff? Or a treble bluff?

This is easier with novels because you can just read to the end and find out...