Amongst the government’s constant rhetoric about Britain’s free-trade utopia, it is often far too easy to forget that Brexit is not just about trade.

In fact, given that we have a former home secretary as prime minister, the impact of our leaving the European Union on security and home affairs matters has been cynically and dangerously underplayed.

It is important to remember that in 2014, it was Theresa May herself who opted-in to the 35 EU justice and home affairs measures, arguing that without them we "would risk harmful individuals walking free and escaping justice, and would seriously harm the capability of our law enforcement agencies to keep the public safe." I couldn’t have put it better myself.

It is therefore very clear—the failure to adequately safeguard these vital measures, which have been so important for our country’s security, could have a catastrophic effect for the safety of everyday citizens in the UK.

Measures such as Europol, the Schengen Information System, and the European Criminal Records Information System (ECRIS) have allowed British authorities to successfully co-ordinate investigations involving cross-border serious and organised crime. The European Arrest Warrant alone has been used to bring 800 British fugitives back to face justice in the UK, including 41 wanted for murder, 61 for rape, and three for terrorism.

Yet, with the government vehemently pursuing its intention to remove Britain from the rulings of the Court of Justice of the European Union (CJEU) and confirming this week that we won't have access to the European Arrest Warrant without a parallel deal on trade and security, the likelihood of achieving a deal which is as effective in keeping British citizens safe is increasingly unlikely.

The negotiation surrounding data exchange between police and intelligence agencies is also likely to be particularly challenging. Currently, access to law enforcement databases is reliant upon the commitment of the UK and the EU to a set of certain safeguards. Following Brexit, the UK will need to demonstrate that our data protection standards are "adequate" in comparison to the EU’s, in order to ensure the exchange of personal data adheres to the correct protections and standards.

In the event of failure in this regard, the UK could be liable to a CJEU ruling that invalidates the transfer of data, as was seen in 2015 with the EU-US "Safe Harbour" agreement. Interestingly, this ruling judged that the US practices of mass data retention and sharing with law enforcement were invalid. This could create potential problems along the road for the Investigatory Powers Act and its insistence on the storing of Internet Connection Records that the Liberal Democrats fought so hard to remove from the bill last year.

Furthermore, our lack of influence in future EU policy making means that when the EU decides to change data protection directives, the UK will have to comply if it is to continue to have access to data exchange, even though we will no longer have no say over those changes.

It will be vital in the upcoming negotiations for the UK to demonstrate that our data protection standards are strong enough to permit UK police access to EU law enforcement databases. Any failure to secure this will put the safety of British citizens at risk.

This is of course now the challenge for Theresa May.

Only this week, a row ensued after the prime minister appeared to blackmail the EU that she would pull security co-operation unless the EU agrees a trade deal. Not only did this shed light on the government’s ludicrous suggestion that no deal would be better than a bad one, but it set an ominous tone for what will be an incredibly important and also delicate negotiation period.

Losing the influence of the UK over the direction of the EU's justice and home affairs measures is now regrettably inevitable. However, I and my Liberal Democrat colleagues will work tirelessly to ensure that the government secure a deal that guarantees the safety of British citizens as a first priority.

Brian Paddick is a Liberal Democrat peer and retired police officer.