A historic signing at RAF Northolt

British Prime Minister Keir Starmer and Polish Prime Minister Donald Tusk signed a new defence and security treaty at RAF Northolt in west London on Wednesday, 27 May 2026. The ceremony included a visit to the nearby Battle of Britain Bunker, where the two leaders laid a commemorative wreath honouring Polish airmen who died defending the United Kingdom during the Second World War. Starmer described the agreement as a "generational uplift" in bilateral relations, while Tusk called the signing a "historic moment" for both nations.

“There's no greater challenge for either of our countries than the challenge of Russian aggression, and we see that not just in Ukraine itself, but beyond Ukraine, impacting on our own countries.”

Naming the threat

A defining feature of the Northolt Treaty is its explicit language on Russia. The text identifies Moscow as "the most significant long-term threat" to Euro-Atlantic security and underscores the need to counter its malign actions. Cezary Tomczyk, Poland's deputy defence minister, confirmed the document includes clear provisions on military assistance in case of threat, technology transfer, and cybersecurity cooperation. Tusk reinforced this stance before departing for London, stating that both parties view Russia as a strategic, long-term danger to Poland, the UK, and NATO.

“Both parties underline that Russia is a strategic threat — and a long-term one — for Poland, for the United Kingdom, for NATO, and therefore our cooperation should focus on securing Poland and other countries against the Russian threat.”

Weapons, borders, and cyber defence

Beyond the political messaging, the treaty lays out concrete industrial and security commitments. The British government said the two countries will combine expertise and industrial capacity to lead the development of complex weapons, including new sophisticated munitions and the co-production of a medium-range air defence missile. The agreement also targets border security, organised crime, and irregular migration through a new joint action plan that includes targeting smuggling gangs' use of social media, maximising intelligence sharing, and deploying new monitoring technologies. A significant portion of the treaty focuses on cybersecurity, reflecting Poland's concern that its role as the main logistics hub for Western military aid to Ukraine has made it a prime target for Russian espionage, cyberattacks, and disinformation campaigns.

A web of European defence pacts

The UK-Poland treaty is the latest in a series of bilateral defence agreements reshaping Europe's security architecture. Britain previously signed similar deals with France and Germany, while Poland concluded a defence treaty with France in 2025 and is working on one with Germany. These pacts come amid sustained pressure from US President Donald Trump's administration for Europe to assume greater responsibility for its own defence. Starmer's government has framed the agreements as part of a broader effort to repair relations with European partners damaged by Brexit nearly a decade ago.

“History teaches us, and geography demonstrates in a particularly painful way, that Poland must forge credible alliances that, above all, deter potential aggressors.”

Scepticism from defence experts

Not all observers are convinced the treaty marks a transformative shift. Ed Arnold, a defence adviser at The D Group and senior associate fellow at the RUSI think tank, questioned the pact's practical impact, noting that previous bilateral agreements between the UK and Poland dating back to 2018 had not fundamentally altered the defence landscape. Tusk himself acknowledged that such alliances do not replace or supplement NATO but rather reflect Warsaw's understanding of a new geopolitical reality in which the United States plans to reduce its presence in Europe.

“Quite frankly, specifically this one, not really.”