Turmoil and terrorism in the Middle East are as grave a security threat to Europe as that posed by the Soviet Union during the cold war, the former head of MI6, the British secret intelligence service, has warned.

Violent attacks on European soil are both more difficult to interrupt than ever before and more likely to occur, Sir John Sawers told the Financial Times in his first interview since leaving office in November.

The Charlie Hebdo murders in Paris and the spate of terror warnings and clampdowns on Islamist extremists around Europe were a wake-up call to the “heightened threat”, said the 59-year-old former spy chief.

“The rigidity we had on Europe’s doorstep for two or three decades posed a set of problems and now the turbulence we have got on Europe’s doorstep is posing another set of problems — in a sense more acute ones because the ­disorder in Syria, Iraq, Libya and Yemen creates a whole series of challenges for us,” said Sir John.

Thousands of Europeans fighting with extremist organisations such as the Islamic State of Iraq and the Levant (Isis) and al-Qaeda were “the vector for the transmission of that terrorist threat to Europe”.

They represent a more serious terrorist threat than ever before because they are “a thousand miles closer to Europe than they were in Afghanistan [and because] they are learning from their own experience and adopting cruder tactics — mass casualty attacks rather than dramatic 9/11-style attacks”.

While he described Syria as the “centrepiece” of the problem, he added that the entire Middle East was at a critical juncture.

“We should be worried about the entirety of the region,” he said, citing the collapse of stable governments in many countries, the dramatic fall in the oil price, the policy uncertainty posed by the Saudi king’s failing health and the fraught international negotiations with Iran over its nuclear programme.

Sir John – a former senior diplomat and expert on the Middle East who is to take up a new role as chairman and partner at Macro Advisory Partners (MAP), a geopolitical risk consultancy firm – also gave warning that with the world’s attention focused on Iraq and Syria, countries such as Libya and Yemen were becoming new terrorism hotspots.

“At the moment, most of the conflict in Libya is internally focused . . . but obviously there is an environment there that could be conducive to terrorist organisations. There is a serious problem in the south. Every effort needs to be made to try to stabilise the country before that threat spreads elsewhere.”

He acknowledged that there were limits to the action western governments could take.

“One of the lessons of the last 15 years is that the west can’t impose new solutions on these countries. They have to find their own way forward.”

Speaking of the terror threat and the debate over surveillance of communications, Sir John said there should be restrictions on the ­availability of totally encrypted communications that are inaccessible to governments.

“We’ve never wanted to have no-go areas for the police in our communities but [totally private means of communication] would be creating no-go areas for evil doers of any sort online — terrorists, criminals, paedophiles — to carry out their business.”

He added: “In a free society, you can’t have absolute security, and in a secure society, you can’t have totally unalloyed freedom. There has to be some compromise and you want to maximise them both.”

Sir John said he believed that such complex new issues were the tip of sweeping broader challenges that would face governments and large companies in the coming years.

“The world is much harder to predict. It’s much harder to navigate your way through the fragmentation of power and politics and ideas,” he said, citing such problems as one reason he decided to join MAP.

“The volatility that we are seeing in global markets is linked to this fragmentation of global politics — and that is new. That is not something we have seen in the past century.”

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