The Manchester attack may boost efforts to preserve long-standing British-EU intelligence sharing following Brexit, even if some forms of cooperation are affected by Britain leaving, experts say.
British Prime Minister Theresa May irked many in Europe when she warned that Britain, the biggest military power in the EU and a nuclear-armed NATO member, might hold back on security cooperation if it can't get a good deal.
The suicide bombing then prompted French President Emmanuel Macron to call for bolstering European counter-terrorism cooperation, even as the European Union and Britain prepare to launch Brexit negotiations next month.
But Steve Peers, a professor of European law at the University of Essex, thinks the attack that killed 22 people in the northern English city may make such a risk even more remote.
"It's possible that the UK would be less likely to threaten the goal of security cooperation because there are cross-border elements that we know of in this case," Peers told AFP.
Security services have identified the bomber as Salman Abedi, a local man of Libyan origin who may have been radicalised in Syria, a stronghold for the Islamic State group, which claimed responsiblity for the attack.
French Interior Minister Gerard Collomb told French television the suspect "grew up in Britain and then suddenly, after a trip to Libya and then likely to Syria, became radicalised and decided to carry out this attack".
Peers added it is "maybe a little less credible to threaten to end this cooperation in light of a fairly recent attack".
He pointed out that much counter-terrorism cooperation happens outside EU channels.
Arnaud Danjean, a member of the European Parliament who worked for the DGSE, France's foreign intelligence service, dismissed fears of a breakdown in intelligence cooperation as overblown.
"European counter-terrorism cooperation is the preserve of national agencies and intelligence services on a bilateral or trilateral basis rather than in a centralised way," Danjean told AFP.
"It does not go through Brussels. Therefore Brexit will not have an impact on that," he added.
For Danjean, the diplomatic hazards of the Brexit negotiations will change nothing there.
And even when France sharply opposed US president George W. Bush's invasion of Iraq, the counter-terrorism relationship endured.
"Channels remained open," he said.
An expert from an EU member state said on condition of anonymity that the intelligence community cannot integrate into an EU framework for reasons of sovereignty, but has other channels to share information.
He said the intelligence services of Britain and other European countries trade information directly without going through a dedicated EU agency.
"It's a vital form of counter-terror cooperation and it will continue quite normally," he added.
However, Britain's departure from the 28-nation bloc could still undermine the work of EU bodies that centralise information exchange on police and judicial cooperation.
"It's hard to say how much or what exactly it means, but I think it's certain that in general there'd be some degree of reduction in security," Peers said.
In 2015, Britain also joined the Schengen Information System (SIS II), an EU-wide database of real-time alerts which is particularly useful in tracking suspected foreign fighters returning from Syria and Iraq.
"Usually, the system is not accessible to a third country. So I do not know how we will manage after Brexit," a European security expert said on condition of anonymity.
Britain also makes use of the European Arrest Warrant (EAW), which speeds up extradition requests, and the Passenger Name Directive, which allows potential criminals to be tracked on flights across the continent.
It is also a major contributor to the European police agency Europol, which headed by Briton Rob Wainwright, who supports EU countries in the fight against organised crime and terrorism.
"It's there that Brexit can have an impact," Danjean said, adding Britain's withdrawal from such agencies or structures could affect resources and operations.
"Nonetheless, third countries can have deals with these agencies. The Americans contribute to Europol, for example," he added.