We are in a new era of threat which demands a new era for defence. Yesterday I, together with my French counterpart Minister Sébastien Lecornu, agreed on implementing the detailed direction for rebooting the Lancaster House defence and security treaties between the United Kingdom and France. With the Lancaster House treaties originally signed in 2010, this reboot will modernise and build on our bilateral defence and security relationship in order to affect a generational shift in both our bilateral co-operation and our joint contribution to the defence of Europe, of its citizens and of its interests. It fulfils a commitment from the countries manifesto and the SDR which states that the UK’s defence relationship with France is “fundamental” to our security.
The UK and France, as Europe’s only nuclear powers, share a special responsibility for European and international defence and security. Our two nations represent nearly 40% of the defence budget of European allies, and more than 50% of the European spending on research and technology.
This reboot of the Lancaster House treaties builds on this strong foundation between the UK and France, reflecting the continuation of our shared values and strategic interests. It will enable us to continue to protect our shared interests, values, partners in Europe and beyond, and, fundamentally, our democratic way of life.
The reboot will deepen our long-standing and resolute commitment to co-operation on nuclear deterrence. Since 1995, we have stated that we do not see situations arising in which the vital interests of one could be threatened without the vital interests of the other also being threatened. Thirty years on, the Northwood declaration, signed by the Prime Minister and the President at the 2025 UK-France summit, states for the first time that our respective deterrents are independent, but can be co-ordinated, and that there is no extreme threat to Europe that would not prompt a response by our two nations. Any adversary threatening the vital interests of our nations should know that they could be confronted by the combined strength of the nuclear forces of both nations.
The UK and France will improve co-ordination across defence nuclear policy, capabilities and operations, and strengthen our ability to make joint decisions if needed. We will also deepen co-operation on nuclear research and technology, building on the 2010 Teutates treaty. A new UK-France nuclear steering board will be established to provide political direction for our collaboration. Both the UK and France remain committed to article V of the North Atlantic treaty and are dedicated to burden-sharing on wider nuclear deterrence. Only the Prime Minister can authorise the use of the UK’s nuclear weapons. The UK’s strategic nuclear forces remain fully operationally independent and sovereign, but we are able to co-ordinate with France should the situation demand it. Our deterrent remains declared to the defence of NATO. We remain committed to our obligations under the NPT to pursue effective measures relating to nuclear disarmament, and to the long-term goal of achieving a world without nuclear weapons.
The reboot will overhaul the existing Combined Joint Expeditionary Force into the Combined Joint Force to refocus it on the Euro-Atlantic and warfighting at scale to deter, placing it on an operational footing for the first time. This will be done through increasing the declared joint force capacity for a deployment of a combined corps capability as the land component of a broader joint force combining all military functions, as part of NATO or on its own. This will also provide for the creation of a joint operations cell, refreshed governance structure and a new strategic alignment process to better co-ordinate our forces.
The reboot will establish an “Entente Industrielle” to enhance capability and industrial co-operation, bringing our defence industries and militaries closer than ever before to strengthen NATO and grow our economies. We will develop capabilities such as the future cruise anti-ship weapon, acquire new Storm Shadow and Scalp missiles, strengthen our co-operation on complex weapons and include other European allies where appropriate. We will expand our co-operation across the new domains of space and cyber and we will also reinvigorate and expand our co-operation on wider science and technology and innovation co-operation, including on artificial intelligence.
In the land domain, we will develop together the UK and French combined corps concept in order to better jointly support NATO defence, and strive to facilitate aligned training at brigade, divisional and corps level to drive interoperability. In the maritime domain, we will expand our existing global maritime security dialogue at defence ministries level and global maritime domain awareness co-operation to better deter maritime hybrid threats, as well as continue to co-ordinate our carrier strike group deployments, including with other European carrier nations through ECGII and NATO. In the air domain, we will increase the complexity of our training exercises and enhance development of counter unmanned aerial systems.
The UK Government remain steadfast in their commitment to the defence of the United Kingdom and our allies; we are confident that the reboot of the Lancaster House treaties will contribute to the security, growth and prosperity of both our nations and the wider European region. We look forward to working closely with France to ensure its successful implementation.
As with the original 2010 treaties, this reboot will continue to serve as the cornerstone of our defence and security relationship with France and will be implemented by both the Ministry of Defence and the Foreign, Commonwealth and Development Office. This reboot of our defence and security relationship marks a significant milestone in strengthening co-operation with France, particularly in a time where the threats we face have changed fundamentally. It is ever more crucial for us to work closely with our allies and partners to strengthen the security of the Euro-Atlantic region, as well as wider global arenas.
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