KEY JUDGEMENTS
-
The UK–Norway Lunna House Agreement strengthens long‑term ASW capacity in the GIUK gap.
-
CUI protection is becoming more complex as undersea infrastructure expands.
-
Russia is likely to continue grey‑zone seabed activity regardless of the outcome in Ukraine.
-
Deterrence by presence alone is increasingly insufficient and may escalate tensions.
-
Autonomous systems will be central to NATO’s future undersea posture.
Overview
In December 2025, the UK and Norway signed the Lunna House Agreement, committing to operate a joint fleet of Type‑26 anti‑submarine frigates in the North Atlantic. The fleet will patrol the strategically vital GIUK Gap to track Russian naval activity and protect critical underwater infrastructure (CUI), including subsea cables and pipelines. Alongside the joint fleet, the agreement includes several measures to deepen defence cooperation: UK participation in Norway’s programme to develop motherships for uncrewed mine‑hunting and undersea warfare systems; year‑round Royal Marine training in Norway; Royal Navy adoption of Norwegian naval strike missiles; expanded collaboration on Sting Ray torpedoes to strengthen munitions stockpiles; joint wargaming; and a shared commitment to lead NATO’s adoption of autonomous systems in the High North.
Why now?
The agreement reflects growing concern within NATO about the vulnerability of CUI following several recent incidents. It builds on the creation of the Maritime Centre for Security of Critical Undersea Infrastructure in 2024, the launch of Baltic Sentry, and the Joint Expeditionary Force’s activation of Nordic Warden. A recent report by the Joint Committee on the National Security Strategy highlighted the Royal Navy’s limited number of Type‑26 frigates as a barrier to deterring sabotage. By combining the UK’s eight Type‑26s currently in production with the five ordered by Norway, the agreement aims to address this capability gap.
The arrangement also reflects NATO’s broader push to integrate forces under the Deterrence and Defence of the Euro‑Atlantic Area (DDA) framework, which assigns regional responsibilities and emphasises interoperability. With both navies tasked with the same region, Norway’s decision to procure Type‑26s from the UK enhances alignment in equipment, maintenance, and operational practice. Operating as a single force will help both navies build familiarity and improve their ability to respond jointly in a crisis—an essential requirement for effective deterrence in the North Atlantic.
Going forward
As undersea cable infrastructure expands over the next decade, protecting CUI will become increasingly complex and will require a blend of crewed and autonomous systems. Despite optimism from some in the cable industry, it is unlikely that sabotage attempts will diminish even if the war in Ukraine ends on terms favourable to Moscow. Russia’s grievances with the UK and NATO, combined with the strategic value of grey‑zone operations, make CUI interference an attractive tool for disruption and capability development. The Lunna House Agreement is therefore a forward‑looking step, particularly in its emphasis on autonomous systems, which will be central to countering future threats—including potential sabotage by uncrewed platforms. It also supports the Royal Navy’s long‑term ambition to establish an “Atlantic Bastion.”
However, questions remain about the long‑term effectiveness of deterrence based on “presence and monitoring.” In 2024, the suspected Russian spy ship Yantar was detected loitering over CUI and was shadowed by multiple UK assets, yet returned a month later and even aimed a laser at patrol aircraft. The Joint Committee on the National Security Strategy has expressed scepticism about whether monitoring alone can deter sabotage when attribution is the only consequence. This raises doubts about how effective the joint fleet will be in deterring future activity.
Presence‑based deterrence also carries escalation risks. In May 2025, the suspected shadow‑fleet vessel Jaguar approached the EstLink subsea power cable, prompting an Estonian military response and the involvement of a Russian SU‑35, which briefly violated Estonian airspace and triggered a NATO scramble. The GIUK Gap is strategically important to both NATO and Russia, and increased activity raises the risk of confrontation and unintended escalation.
In the short term, the Lunna House Agreement signals political recognition of the growing importance of CUI and reflects wider European concern about deteriorating relations with Russia. It forms part of a broader effort to rebuild defence capabilities, address hybrid threats, and prepare for potential future conflict.