The RAND Europe submission to the UK Parliament’s Joint Committee on National Security Strategy, in response to its Call for Evidence on Undersea Cables dated 6 March 2025, presents a detailed and urgent assessment of the risks, vulnerabilities, and governance challenges surrounding critical undersea infrastructure—particularly the telecommunications cables upon which modern society fundamentally relies. These cables, largely invisible and buried deep on the ocean floor, carry over 97 percent of global telecommunications and enable trillions of pounds in daily financial transactions. For the United Kingdom, an island nation positioned at the nexus of transatlantic data flows, their strategic importance is paramount and only set to increase over the next decade.
Despite the availability of alternative technologies, such as satellite communication, none offer comparable bandwidth, speed, or reliability. As the digital economy expands and more sectors—from finance to defence, from healthcare to energy—rely on instantaneous data exchange, the number of subsea cables is expected to grow. Yet, with this growth comes greater vulnerability. These infrastructures are physically exposed, technically complex, and legally fragmented. Most are simply laid on or buried shallowly under the seabed, and landing stations on shore often remain inadequately protected. Their sheer geographical scale makes constant monitoring unfeasible with current assets, especially given the strain on naval and surveillance resources.
The threat landscape is evolving. While most cable disruptions still result from accidents—such as trawling, anchoring, or natural events—there is growing concern over the strategic interest that hostile actors show toward these networks. State actors, particularly Russia and China, possess the means to carry out targeted sabotage or covert espionage operations on undersea infrastructure. Russia’s use of ‘ghost fleets’ and intelligence-gathering vessels in European waters has raised alarm. China’s growing influence through ownership stakes in European cable companies has also prompted concern. Moreover, technological diffusion is lowering the threshold of entry for less capable states and non-state actors—terrorist groups, criminal organisations, hackers—who can now access uncrewed underwater vehicles (UUVs) or launch cyberattacks on increasingly digitised cable systems.
What complicates the picture further is the legal ambiguity governing the high seas, where many cables run. Jurisdictional gaps, fragmented governance, and the transnational nature of ownership make the attribution of sabotage difficult and responses politically delicate. Hybrid or ‘grey zone’ tactics—those falling below the threshold of open warfare—exploit precisely this ambiguity, allowing actors to sow disruption without consequence.
The UK, however, is not without assets. It hosts NATO’s Maritime Centre for the Security of Critical Undersea Infrastructure and plays a leading role in the Joint Expeditionary Force (JEF), which includes rapid response protocols and maritime patrols such as Operation NORDIC WARDEN. The Royal Navy has also acquired the RFA Proteus, its first Multi-Role Ocean Surveillance ship, although operational delays have hampered its deployment. The UK’s industrial and academic base, notably in offshore engineering, artificial intelligence, and robotics, places it in a strong position to pioneer protective technologies.
Still, resilience remains a concern. Disruptions to cables—even temporary—could have cascading effects across the economy, from halting financial transactions to crippling energy systems. The RAND analysis quantifies the economic cost of disruption: up to €24 million per day for a telecom cable, and significantly more for oil and gas pipelines, whose repair can take months. With limited numbers of repair vessels and highly specialised equipment, a large-scale or coordinated attack could overwhelm existing response capabilities.
The report criticises the current governance framework for being too diffuse. Responsibility for cable security is split among various UK departments—Science and Technology, Energy Security, Defence—and across public and private actors. Coordination remains patchy, with information sharing hindered by institutional barriers, concerns over reputational risk, and classified intelligence protocols. As a result, vulnerabilities persist, both in technical terms and in the mechanisms for response and deterrence.
A key recommendation is the need to rebalance priorities between enhancing domestic resilience and improving detection and deterrence. Relying solely on crewed naval patrols is neither efficient nor sustainable. The report advocates for greater investment in uncrewed systems, advanced sensors, AI-enabled monitoring, and, crucially, a reallocation of responsibility to the private sector. Infrastructure operators should adopt a duty of care, integrating security by design and engaging proactively with public authorities in strategic planning and real-time threat detection.
In sum, the protection of undersea cables—and critical underwater infrastructure more broadly—must be understood not merely as a defence concern, but as a systemic issue of national resilience and international cooperation. A coherent, well-funded, and technologically sophisticated approach is now required to defend what has become one of the most invisible yet indispensable backbones of global security and economic stability.