A no - deal Brexit would mean the UK loses access to key EU crime - fighting tools , affecting safety and security , according to the UK 's head of counter - terrorism , Neil Basu . Security systems would be slower , he said , and no contingency planning could adequately replace the loss of access to shared intelligence databases and European arrest warrants and passenger lists in a no - deal scenario . This could mean UK authorities are not alerted when serious offenders or wanted people enter the UK . The three key measures are fast access to intelligence and data through the Schengen Information System II database, as well as passenger name records, and the ability to use European arrest warrants. Basu , however , expressed confidence that UK politicians grasp the key issues at hand .
A no - deal Brexit would mean the UK loses access to key EU crime - fighting tools , affecting safety and security , according to the UK 's head of counter - terrorism , Neil Basu . Security systems would be slower , he said , and no contingency planning could adequately replace the loss of access to shared intelligence databases and European arrest warrants and passenger lists in a no - deal scenario . This could mean UK authorities are not alerted when serious offenders or wanted people enter the UK . Basu , however , expressed confidence that UK politicians grasp the key issues at hand .