“The military defeat of the caliphate does not represent the end of the terrorist threat that we face,” he said. “You can’t use military force to kill and idea.”
Mr Younger warned that Isil was already in the process of trying to grow elsewhere around the world, even as its fighters are defeated in Syria, and that the threat from al-Qaeda had not been completely extinguished.
He said: “Daesh [Isil] is a resilient organisation and it is reorganising, returning to its natural state as an asymmetric transnational terrorist organisation. We see it morphing, spreading out.
“Al-Qaeda…has undergone a certain resurgence as a result of the degradation of Daesh and it is a force that should also be taken seriously. It is definitely not done out, and is something we should remain focused on.”
Mr Younger was keen to stress the “strength and unconditional nature of the UK security offer” and said Brexit would not harm enduring partnerships.
“Britain’s commitment to the security of the European continent is unconditional,” he said. “Our aim is to strengthen our security partnerships in Europe, alongside our other intelligence partnerships across the globe, because that is the inescapable logic of a world of increasingly international hybrid threats.”
The ability to “operationalise” partnerships with other intelligence organisations was critical in preserving our way of life, he said, and was used to great effect after the nerve-agent attack in Salisbury last year.