Europol is on track to become the first EU body to get a taste of life without the U.K. as a direct result of Brexit.

Britain must decide in the coming months if it wants to sign up to new rules expanding the European law enforcement agency's powers to fight terrorism, or opt out — and lose access to hundreds of databases, which hold information ranging from vehicle license plates, guns and organized crime to foreign fighters and terrorism suspects.

“The choice to opt in or out of Europol will be a big political and constitutional test for the U.K., a sort of pre-Article 50 test,” said Claude Moraes, the British Labour MEP who chairs the European Parliament's committee on civil liberties, justice and home affairs (LIBE).

Britain has been a vital contributor to Europol and the EU would be keen to retain its capabilities in intelligence and policing once Brexit is implemented. With the appointment last week of Britain's Julian King as commissioner in charge of the security union, the Commission created a new portfolio specifically designed to play to the U.K.'s strengths in counter-terrorism.

The issue now is whether Britain returns the compliment by showing continued commitment to Europol, or would rather live in splendid isolation, "taking back control" — in the words of the Leave campaign — of security policy under the prime ministership of Theresa May, who was home secretary from 2010.

"Both King and May will want to remain part of Europol. However, leaving it might be part of the price we are paying for the profound and major referendum vote," said Moraes.

Cooperation is the way forward when it comes to counter-terrorism, so from a practical perspective it would make sense to be part of Europol — Raffaello Pantucci, counter-terrorism expert at the Royal United Services Institute

Europol's new powers, approved in the wake of the terror attacks in Paris and Brussels, take effect from May 2017. Agreed by EU countries and the European Parliament just before the U.K. referendum, these will give MEPs greater powers of scrutiny over Europol while encouraging national governments to share more information with the Hague-based agency.

In future it should be easier for Europol to set up specialized units, or focal points, to respond to emerging threats in terrorism and serious crime, making it faster "to get things done," according to a Europol official.

Last year, U.K. authorities initiated 2,500 cases for cross-border investigation and operational support at Europol, according to data from the agency obtained by POLITICO — meaning Britain has one of the highest rates of engagement in the EU.

"The U.K. is also one of the leading sources of intelligence contributed to Europol's databases on serious and organized crime," said a spokesperson for the agency, adding that senior British law enforcement officers are leading key projects in a four-year action plan to improve cooperation between national agencies in this area, a project known as the EU Policy Cycle.

Europol's British director, former MI5 intelligence analyst Rob Wainwright, argued repeatedly before and after Brexit that both the EU and the U.K. stand to benefit from maintaining this level of cooperation on security. He estimates that 40 percent of all Europol cases have some level of British involvement.

Follow the Danes

"Cooperation is the way forward when it comes to counter-terrorism, so from a practical perspective it would make sense to be part of Europol," said Raffaello Pantucci, counter-terrorism expert at the Royal United Services Institute in London. "However, the agency became a feature of the Brexit debate, and I assume that the politics of it will be more complicated in the coming months."

Despite Wainwright's campaign, and a growing terrorism threat that is spreading across the 28-nation bloc, the most likely outcome is that the U.K. will seek an opt-out, according to POLITICO's conversations with half a dozen senior officials in the security and home affairs sphere in London and on the Continent.

Following Britain's vote to leave the EU in the June referendum, European justice and home affairs officials met in Brussels to discuss, among other topics, the future relationship between the U.K. and Europol.

"The Brits made it clear they have no intention of opting in, and that they will seek a special agreement like the Danes," said a senior EU diplomat with knowledge of the meeting. The diplomat said that renewing the U.K.'s membership of an EU agency while preparing its withdrawal from the Union would send a contradictory message, in Britain and across the bloc.

Danes voted in a referendum last December to quit Europol from May 1, 2017, but the Danish government has since submitted a request to the European Commission for a special arrangement with Europol, as well as the judicial cooperation body Eurojust and the EU's Passenger Name Record directive, to avoid being completely cut off from its European partners from next year.

"We're clear though that while we are leaving the EU, cooperation on security and law enforcement with European (and global) allies will continue" — senior U.K. government official

More than three months after the request was sent the Danes are still waiting for a reply, according to a Danish official.

"The request is currently being reviewed," said a Commission spokesperson.

If Brexit means Brexit

So far, there is little consensus within the U.K. on the value of Europol.

Richard Dearlove, who ran the U.K.'s foreign intelligence agency MI6 from 1999 to 2004, attacked Europol in an op-ed ahead of the Brexit referendum, saying the 28 members of the EU had "vastly varying levels of professionalism in intelligence," and that the agency's meetings always had to accommodate the "slowest and leakiest ship."

On the other hand, Lynne Owens, director-general of the National Crime Agency which deals with global and domestic crime threats, said ahead of the vote: "It would be more difficult if we could not share information in an agile way, and at the moment that happens within the European Union mechanism."

Leaving aside the different perspectives among former and serving security officials, any decision to remain in Europol once its powers are expanded next year is bound to be problematic because it would implicitly challenge the premises of Brexit.

Once Article 50 is activated and Britain negotiates its departure from the EU, it will no longer recognize the European Parliament's authority over its legislation and national policy, and will have no say in future changes to Europol's powers and structure.

"The government has to still take a decision on this," said a senior U.K. government official. "We're clear though that while we are leaving the EU, cooperation on security and law enforcement with European (and global) allies will continue."

"We'll do what's necessary to keep our people safe," added the official.