It would be "unthinkable" for Britain to depart the EU without a deal on security, a former head of the bloc's law enforcement agency has said.
Sir Rob Wainwright, who left Europol in May after nine years as executive director, told MPs he expects the two sides to reach an agreement.
Although it is a complex and unique situation, he said he detected an understanding that "we have to get this right, that literally people's lives depend on it".
A host of EU measures and tools have come under scrutiny following the referendum in 2016.
Senior figures have highlighted the role played by the European Arrest Warrant, a legal framework introduced to speed up the extradition of individuals between member states; the Second Generation Schengen Information System (SIS II), a database of real time alerts; Europol; and the European Criminal Records Information System (ECRIS).
The Government is seeking a bespoke deal on security co-operation with the EU after Brexit.
A blueprint published last year called for a comprehensive framework to be underpinned by a new treaty.
Sir Rob told the Commons Home Affairs committee: "This is a complex business. You will have noticed that Brexit is not an easy path to follow.
"There is in this space a very complicated set of political, legal and even operational issues to overcome and navigating those is not easy, is not proving to be easy, and I think we still have further difficulties to get through.
"But at least we start, I think, from the perspective of wanting to get the right security deal in place, and I can't imagine there will be a no security deal at the end of this process.
"Frankly, that's unthinkable."
Sir Rob's remarks chime with the message from within the UK policing and intelligence community.
In recent weeks the heads of MI5 and GCHQ have both highlighted the importance of maintaining close security links between Britain and European partners.