UK-Germany Kensington Treaty: How London and Berlin Are Building Europe’s New Defense Axis Against Hybrid Threats

The immediate circumstances are difficult to ignore. The announcement, formalised during talks in Berlin on 8 October, follows a series of escalating incidents. In September, German authorities accused Russia of launching an explosive-laden drone at Leipzig/Halle Airport, a major freight hub also used to transfer aid to Ukraine. Moscow denied involvement. British officials have separately confirmed that Russian naval and auxiliary vessels have been mapping undersea telecommunications cables, gas pipelines and offshore wind installations in the North and Baltic Seas.

These are different kinds of activity, but they expose the same vulnerability. Europe's security depends on infrastructure that crosses national borders, operates far from shore and often sits beyond the reach of straightforward enforcement. The new British-German partnership is an attempt to bring the intelligence and operational response closer to the scale of the threat.

The problem with defending the space between peace and war

Hybrid operations exploit uncertainty. A damaged cable may disrupt communications without producing an obvious military confrontation. A vessel can survey sensitive infrastructure while appearing to conduct legitimate commercial or scientific activity. Cyberattacks, covert surveillance and sabotage can impose costs on European governments without providing an unambiguous justification for military retaliation.

Russia is the principal threat identified by British and German officials in the current campaign, although the partnership's public mandate covers hostile hybrid activity regardless of its origin.

The difficulty is not simply detecting suspicious behaviour. It is establishing responsibility, gathering evidence and determining what action is legally available. Intelligence assessments may point towards a hostile operation, but suspicion does not automatically establish criminal liability. Nor does damage to infrastructure in international waters necessarily give a coastal state jurisdiction to prosecute those responsible.

A Finnish court brought this problem into sharp focus on 9 October, when it dismissed criminal charges against the tanker Eagle S over undersea cable damage because of jurisdictional limitations. The ruling exposed the distance between identifying a potential security threat and securing a legally enforceable response.

For European governments, that gap is strategically significant. Deterrence becomes harder when an adversary can impose costs while exploiting uncertainty over attribution, jurisdiction and the threshold for military action.

The Kensington Treaty cannot, by itself, resolve those legal constraints. Its value will depend on whether closer intelligence cooperation enables Britain and Germany to identify suspicious activity earlier, connect incidents across jurisdictions and provide evidence that supports effective national or collective action.

From surveillance to protection

The threat to undersea infrastructure has become increasingly tangible. Scandinavian public broadcasters DR, NRK, SVT and Yle have reported on roughly 50 Russian vessels suspected of conducting undersea mapping while disabling their Automatic Identification Systems or transmitting false positions. The vessels included the research ship Admiral Vladimirsky.

Such tactics complicate maritime monitoring. Automatic Identification Systems help authorities establish where ships are travelling, but their usefulness is reduced when vessels switch them off or manipulate the information they transmit. Monitoring must therefore combine vessel movements with other intelligence and surveillance, rather than treating a ship's declared position as definitive evidence of its activities.

The potential targets extend well beyond military installations. Fibre-optic cables carry international communications; gas pipelines and electricity connections support energy security; offshore wind farms are part of the infrastructure on which European economies increasingly depend. A disruption can affect civilian life and commercial activity even when no territory is occupied and no conventional weapon is used.

The British-German agreement commits the two countries to closer strategic and operational cooperation in identifying, monitoring, deterring and disrupting state-sponsored sabotage, cyberattacks, surveillance and threats to critical infrastructure. The practical test is whether this commitment produces a more coherent picture of activity across the North Sea and Baltic, allowing authorities to connect information that might otherwise remain divided between national agencies.

Existing initiatives provide part of the framework. NATO's Baltic Sentry operation has intensified maritime patrols using frigates, maritime patrol aircraft and uncrewed surface and underwater vehicles. The ten-country Joint Expeditionary Force operates Nordic Warden, a system for tracking suspicious vessel behaviour across the North Atlantic, Kattegat and Baltic Sea. The United States has also deployed around 48 Marines to work with Finland's Coastal Brigade on reconnaissance and drone monitoring.

The European Union is approaching the problem from another direction. The European Commission has allocated €5.8 million for regional subsea cable monitoring hubs in the Baltic and Mediterranean and launched a €40 million tender to expand cable repair capacity. Fourteen coastal states have issued legal notices restricting shadow-fleet vessels without clear nationality or valid insurance.

These measures address different parts of the same vulnerability: detection, deterrence, enforcement and recovery. More surveillance is of limited value if authorities cannot act on what they discover. Equally, an effective response to sabotage must include the capacity to repair damaged infrastructure and restore services.

The new bilateral partnership could help connect these elements. But the available commitments do not yet establish precisely how British and German agencies will share operational intelligence, coordinate interventions or divide responsibility during a crisis. Those details will matter more than the language of the treaty.

Britain is returning through security, not institutions

For Burnham, Berlin is also a test of Britain's post-Brexit relationship with Europe. His visit was his first official bilateral trip to Germany and his first official European trip outside Ukraine since becoming prime minister in July.

The political route he is pursuing is notable. Rather than making institutional reintegration the immediate focus, his government is using defence, intelligence and industrial cooperation to restore Britain's position within continental European security.

Merz has welcomed the prospect of bringing Britain closer to Europe. Burnham, meanwhile, has linked security cooperation with economic growth and reiterated his intention to strengthen relations ahead of an upcoming UK-EU summit. French Finance Minister Roland Lescure has gone further in public, urging Britain to return fully to the Union.

The distinction matters. The Kensington Treaty does not bring Britain back into the EU's institutional structures. It creates a framework for closer cooperation between two states whose interests overlap, regardless of Britain's membership status.

That approach may prove more immediately practical than reopening the wider arguments surrounding Brexit. Security threats do not stop at the Channel, and British capabilities remain relevant to European defence. Germany, for its part, has an interest in ensuring that the continent's largest economies can coordinate against risks to infrastructure, trade and industrial capacity.

Bilateral agreements can also move faster than arrangements requiring agreement across a larger group of states. Their limitation is that they can produce overlapping structures unless their responsibilities and links to existing institutions are clearly defined.

The challenge for London and Berlin is to make the partnership complementary to NATO and EU initiatives, not a separate mechanism competing with them for intelligence, resources or political attention.

Defence cooperation becomes industrial policy

The summit's economic agenda points towards a broader ambition. Burnham and Merz convened the first UK-Germany Regional Growth Forum, bringing together business leaders to explore cross-border investment and cooperation in science, space and quantum technology. Burnham also announced plans to host the first joint meeting of the two countries' cabinets in 2027.

The most consequential industrial question concerns the Global Combat Air Programme, the sixth-generation fighter initiative led by Britain, Italy and Japan. Burnham said his government would actively seek to advance Germany's participation.

Germany's potential entry would extend the logic of the security agreement into the defence-industrial sphere. Advanced military programmes require sustained cooperation in technology, manufacturing and investment. Closer links between British and German industry could create additional opportunities for collaboration, while giving the two governments a shared interest in maintaining long-term technological capabilities.

Quantum technology and space cooperation fit the same wider pattern. These are commercial fields, but they also intersect with strategic autonomy, communications and the technologies on which modern security depends. Industrial integration is therefore not merely an economic dividend attached to the treaty. It could become part of the infrastructure of European defence itself.

There are limits to what can be inferred from the announcements. The Regional Growth Forum has established a channel for cooperation, not guaranteed investment or completed industrial projects. Germany's possible participation in GCAP remains a policy objective rather than a settled commitment. Turning political alignment into production capacity will require decisions that extend beyond the summit.

Still, the direction is clear. Britain and Germany are treating economic resilience and security as increasingly inseparable, with cross-border industrial relationships providing another means of binding their strategic interests together.

The deterrence gap remains

The central question is whether Europe can make the costs of hybrid operations sufficiently high without escalating every suspicious incident into a confrontation between Russia and NATO.

Moscow continues to deny Western allegations of sabotage. Russian Foreign Ministry spokesperson Maria Zakharova has said that Russia does not intend to fight Western Europe and threatens no one, while warning that Western actions could provoke retaliation. Such statements do little to settle disputes over individual incidents, leaving European governments to work with intelligence assessments, physical evidence and the limits of international law.

The difficulty is particularly acute at sea, where surveillance may establish patterns of suspicious behaviour without proving that a specific vessel caused specific damage. The Eagle S ruling illustrates how a case can encounter legal obstacles even after an incident has attracted serious security concerns.

European governments are consequently building a layered response: NATO patrols, national intelligence, bilateral agreements, EU infrastructure funding and greater industrial cooperation. Each addresses a different weakness, but their effectiveness depends on whether information can move between them and whether the resulting evidence supports action.

The Kensington Treaty gives Britain and Germany a stronger political basis for that coordination. It does not eliminate the distinction between intelligence and proof, or between a suspicious operation and an act that can be prosecuted. Nor does it guarantee that monitoring will prevent damage to cables, pipelines or logistics hubs.

For European security planners, the unresolved problem is how to turn knowledge of a hostile operation into a timely, proportionate and legally defensible response. A network of surveillance systems can make covert activity harder to conceal. A network of industrial and repair capabilities can make its consequences less severe. Neither, on its own, guarantees deterrence.