The threat of terrorism would increase significantly if there were no Brexit agreement between Britain and the EU, the former head of MI6 said. "The simple answer is yes," John Scarlett, former head of the UK's foreign intelligence service, told <em>The National</em> when asked whether leaving the bloc without a deal increased the risk of a serious loss of intelligence. Mr Scarlett was joined by Julian King, a former EU Security Commissioner, in an online seminar hosted by hosted by the Royal United Services Institute, a security think tank. Britain’s intelligence services, including MI6, domestic intelligence service MI5 and police counterterrorism teams, will lose access to European databases on terrorists and other criminals if there is no formal agreement by December 31. They will be denied access to the crime database Schengen Information System II, which British intelligence services used 570 million times last year, making the country the third-biggest user in the EU. Britain will also be blocked from the European Criminal Records Information Service, which allows quick sharing of records, and Prum, a DNA database used 12,000 times in the past year by UK investigators. Without such combined resources, UK intelligence agencies will struggle to battle terrorism effectively, Mr Scarlett said. “If there is a weakening of data exchange capability then the investigative capability on the part of the EU or the UK potentially weakens our ability to respond” to religious extremist threats. “And in terms of our overall security environment the [religious] extremist threat is absolutely still there.” There are also considerable concerns that the security services will struggle to trail suspects across Europe, especially religious extremists. Mr Scarlett gave as examples the ISIS attacks in 2017 at Manchester Arena and on London Bridge, which killed 22 and eight people respectively. He said the ability to track suspects across European borders, particularly the 26 countries comprising the Schengen zone, would be impeded by a no-deal Brexit. And the tracking of people, finances, ports and analysis of terrorist capabilities was “fundamental to effective counterterrorism work”, Mr Scarlett said. Britain is now entering crucial weeks of trade-deal talks with the EU looking to formalise an agreement before an automatic “no-deal” happens at the end of the year. Doubts remain that a deal will be reached. The seminar heard that without a deal, Britain “almost certainly” will not have access to the high-level databases. “You’re looking at the situation in Iraq and Syria, for example, and the spreading of ISIS into the Sahel and Central Africa,” Mr Scarlett said. “These are very important areas, clearly of relevance to EU and UK security, which maybe don’t get as much attention as they should.” A paper written by Mr Scarlett and Mr King said: “We have yet to talk to anyone involved who does not anticipate some loss of capability. “This is a worry, potentially a very serious worry.”