An Incomplete Renewal: The Case for an Arctic Dimension to the Lancaster House Treaties

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A view of the UK Parliament in Westminster, London, a symbol of British governmental and diplomatic decision-making. Photo: David Zherdenovsky

In July 2025, the United Kingdom and France renewed and modernised the Lancaster House Treaties, the 2010 bilateral framework that has defined Franco-British defence and security cooperation for over fifteen years. The renewal constituted a timely reaffirmation of the relationship between the two states, at a moment of considerable uncertainty in the transatlantic security order. It was also, in one significant respect, a missed opportunity.

The renewed Lancaster House framework contains no Arctic or High North dimension. At a moment when the Arctic is rapidly emerging as one of the defining strategic theatres of the coming decades, the two European nuclear powers and the only European permanent members of the UN Security Council have updated their primary bilateral defence architecture without reference to a region that directly affects both of their strategic interests. While this absence is significant, it is also addressable.

Why France Belongs in the Arctic Conversation

France, much like the UK, is frequently absent from discussions on Arctic security, which may seem logical given their lack of geographical status. However, France has held observer status at the Arctic Council since 2000, reflecting its longstanding scientific and environmental engagement with the region. Its overseas territory of Saint-Pierre-et-Miquelon sits in the North Atlantic approaches, and the French Navy maintains a significant North Atlantic operational presence.

France’s nuclear-powered submarine fleet, which operates under the Lancaster House cooperative framework, patrols waters whose strategic geometry is shaped directly by Arctic dynamics, including the Russian Northern Fleet’s operational patterns and the Greenland-Iceland-UK Gap, through which those submarines must pass.

France has been among the most vocal European advocates for defence autonomy and burden-sharing in the face of uncertain US commitment. If any European state has both the capability and the political will to step forward when it comes to Arctic security, it is France. The institutional mechanism through which it could do so most naturally, given existing arrangements, is the Lancaster House Treaties.

The Gap in the Current Framework

The Lancaster House Treaties, as renewed, cover nuclear weapons safety and cooperation, combined carrier strike operations, joint expeditionary force arrangements, and defence-industrial collaboration. They represent significant bilateral depth, and their renewal in 2025 demonstrated that existing frameworks are adaptable. What the treaties do not cover is any dimension of High North security: no joint Arctic operational doctrine, no Franco-British dialogue on governance, no framework for coordinating positions within the Arctic Council, and no mechanism for the two states to act together coherently on the environmental challenges in the region.

This gap has grown more consequential since the original 2010 text was developed. The current pace of Arctic militarisation, which includes the accelerating opening of northern shipping routes, the deterioration of Arctic Council cooperation since 2022, and the growing uncertainty around US strategic posture in the High North have collectively transformed the Arctic from a peripheral concern to a central one. A bilateral defence framework between the two states that does not address it is logically, therefore, incomplete.

Envisioning an Arctic Mechanism

A Franco-British High North security dialogue, established as a standing working group under the Lancaster House Treaties, would prove substantive if it were to cover merely four key priorities.

First, a joint assessment mechanism on Arctic security, bringing together defence and foreign ministry officials to coordinate positions on High North developments, including Russian militarisation and Chinese Arctic ambitions. Coordination would cost relatively little given both states likely already maintain these capabilities, yet it would deliver strategic coherence.

Secondly, a shared Arctic Council observer strategy, through which France and the UK could act in unison where it proved beneficial to align their positions. Despite close bilateral ties, at present, both states engage the Council independently and without formal coordination.

Third, a mechanism for Franco-British naval cooperation in North Atlantic and High North waters, extending the existing carrier strike and submarine cooperation arrangements into a defined northern operational context. The Lunna House Agreement between the UK and Norway, signed in 2025, demonstrates that bilateral frameworks can incorporate explicit regional security dimensions when the political will exists. Lancaster House should follow that precedent.

Fourth, joint Franco-British participation in Arctic cold-weather training at Camp Viking in northern Norway. The British Royal Marines currently maintain a year-round presence at the facility under the terms of the Lunna House Agreement with Norway, yet Camp Viking remains a temporary leased arrangement whose long-term future is inherently uncertain. French participation in Arctic training at the facility, building on the existing carrier strike and joint expeditionary force arrangements under Lancaster House, would constitute a concrete expression of bilateral Arctic cooperation. This would require Norwegian consent, but Oslo’s interest in deepening High North engagement with its European defence partners makes that a realistic diplomatic conversation rather than an obstacle.

A Window That Should Not Be Missed

The July 2025 renewal represented the first formal update to the Lancaster House framework within fifteen years. The political conditions for a further amendment are unlikely to be more favourable than now. Both governments are currently heavily invested in the bilateral relationship, both face the same strategic uncertainty in the transatlantic order and both have Arctic interests that are underserved by the current framework.

The Arctic is not a peripheral theatre, it is a space in which the decisions taken now, about basing, doctrine, governance, and diplomatic coordination, will define the security environment for the coming generations.

A Franco-British Arctic mechanism under Lancaster House would not solve every challenge but it would, however, ensure that the two states best placed to lead European security engagement in the High North are doing so together rather than separately.

The renewed Lancaster House Treaties are an achievement, but an Arctic annex would make them fit for the strategic realities of the moment.

Anthony Heron is a Research Associate at The Arctic Institute and Managing Editor at Springer Nature’s Humanities and Social Sciences Communications.