In the wake of the raid that killed Abu Sayyaf, suspicions of an undeclared alliance have hardened. One senior western official familiar with the intelligence gathered at the slain leader’s compound said that direct dealings between Turkish officials and ranking Isis members was now “undeniable”.

“There are hundreds of flash drives and documents that were seized there,” the official told the Observer. “They are being analysed at the moment, but the links are already so clear that they could end up having profound policy implications for the relationship between us and Ankara.” …

Turkey has openly supported other jihadi groups, such as Ahrar al-Sham, which espouses much of al-Qaida’s ideology, and Jabhat al-Nusra, which is proscribed as a terror organisation by much of the US and Europe. “The distinctions they draw [with other opposition groups] are thin indeed,” said the western official. “There is no doubt at all that they militarily cooperate with both.”

European officials have regularly said they have gained no traction trying to raise either organisation with Ankara and have long been warned off trying. Isis, though, has gradually been recognised as a force that can no longer be contained or managed. “We can talk about them now,” said a European official in Ankara. “As long as we describe them as ‘those who abuse religion’.