The security and intelligence services have repeatedly stressed they do not want to interfere in the political process, but officials have privately stated their concern about "crashing out" of the EU without issues of security cooperation settled.
In a rare public address, Alex Younger will outline how cooperation with European allies has prevented multiple attacks in the UK and the continent by Isis and other terrorist groups.
While the prime minister's non-binding Brexit declaration sets out plans to maintain similar security provisions to those currently in place, a no-deal Brexit would leave future cooperation in doubt – a scenario security minister Ben Wallace has warned "would have a real impact on our ability to work with our European partners to protect the public".
While stressing the need for continued security cooperation with Europe, Mr Younger will describe how the new industrial revolution in technology is essential for the “fourth generation of espionage” needed to counter threats from terrorists and foreign states who regard themselves as being in a state of perpetual confrontation with us.
In addition to the terrorist threat, countries such as Russia are taking advantage of “the blurred line between the cyber and physical worlds to probe UK institutions and defences in ways that fall short of traditional warfare”, Mr Younger will add.
The MI6 chief will describe how Britain used operational methods, the legal system and international alliances to expose how the Kremlin carried out the attempted assassination in Salisbury and coordinated the expulsion of Russians working under diplomatic credentials in more than a dozen states. MI6, Mr Younger will say, is determined that there is a “cost to malign behaviour”.
Speaking at St Andrews University in Scotland, he will reiterate that: “Russia or any other state intent on subverting our way of life not to underestimate our determination and our capabilities, or those of our allies.”
He is also keen to stress that the UK does not seek to be in eternal conflict with Russia, and would be willing to avoid a confrontation if Moscow is prepared to rethink its aggressive approach. But, according to security sources, Vladimir Putin’s government shows no signs of doing that.
As well as bombings and shootings, Mr Younger wants to highlight the hybrid threat in which Russia, in particular, has used hacking and disinformation offensives to allegedly manipulate elections in the West, as well as the Brexit and Catalan independence referendum votes.
He will describe how MI6 and intelligence agencies are evolving a fourth generation of espionage to meet the threats of the hybrid age: “The era of the fourth industrial revolution calls for a fourth generation espionage: fusing our traditional human skills with accelerated innovation, new partnerships and a mindset that mobilises diversity and empowers the young.”
The fourth generation of espionage is a reference to how the nature of spying has changed from the First World War; the Second War and the Cold War in its aftermath; the scenario after 9/11 and now the combination of hybrid warfare and state sponsored assassinations.
Mr Younger holds that Britain must tap into its diverse community to provide the best defence of the realm.
“I want to speak to young people who have never seen themselves in MI6 ... it doesn’t matter where you are from. If you want to make a difference and you think you might have what it takes, then the chances are that you do have what it takes, and we hope you will step forward,” he will say.
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