Britain has agreed to share classified technical details of its Storm Shadow cruise missiles with Ukraine, a move that could allow Kyiv to begin building the long-range weapons domestically — and one that has drawn a furious response from Moscow.

The announcement came as British Prime Minister Andy Burnham made his first visit to Kyiv since taking office, arriving on the day Ukraine marked the 35th anniversary of its independence. Standing alongside President Volodymyr Zelenskyy, Burnham confirmed that London had cleared the way for European defence manufacturer MBDA to release classified information on British-made components used in the SCALP/Storm Shadow missile system.

What the agreement mean

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Until now, the UK had been manufacturing Storm Shadow missiles directly and supplying finished weapons to Ukraine. Under the new arrangement, Kyiv will instead gain access to the underlying technical blueprints, opening the door to establishing its own assembly lines for the long-range precision weapon — a project Ukraine and France had already begun discussing earlier this year.

Officials say the missiles, which have a range exceeding 250 kilometres, would allow Ukrainian forces to strike hardened targets deep behind Russian lines that are typically out of reach for drones. Analysts note that while transferring blueprints does not translate into instant manufacturing capability, it represents a significant vote of confidence in Ukraine’s long-term ability to sustain its own defence industry.

“The friendship between our two countries will long outlast Russia’s illegal war,” Burnham told a crowd gathered in Kyiv, comparing Ukraine’s resistance to earlier struggles against tyranny in Europe’s history. He pledged that British support “will not waver,” framing the decision as part of a broader commitment to help Ukraine become self-sufficient in producing critical weapons systems.

Moscow’s sharp response

The Kremlin did not take the announcement quietly. Spokesperson Dmitry Peskov said Russia viewed the decision “extremely negatively,” accusing Britain of adding “fuel on the fire” and of deliberately obstructing progress toward any peace settlement. Peskov went further, alleging that Russian forces were already gathering intelligence on potential production sites linked to the missile programme — a statement widely interpreted in Kyiv and London as a thinly veiled threat.

A Kremlin-aligned adviser separately suggested that facilities in the UK involved in manufacturing drones destined for Ukraine could face attacks from “unknown sources,” further escalating the rhetoric surrounding Britain’s expanding role in supporting Kyiv’s war effort.

Burnham, for his part, showed little sign of being deterred. Responding to Moscow’s accusations at a press conference in Kyiv, he pushed back firmly: “Who started the fire? That’s the question, isn’t it.” The remark underscored a broader argument British officials have made — that continued support for Ukraine is a response to Russian aggression, not a provocation in itself.

Escalating tensions between London and Moscow

The missile announcement lands against a backdrop of rapidly deteriorating diplomatic relations between the UK and Russia. Just days earlier, Moscow confirmed the departure of its ambassador to Britain, a move seen by observers as symbolic of the increasingly frosty state of bilateral ties.

Officials in London have argued that Russia’s angry reaction is, if anything, evidence that British assistance to Ukraine is having a tangible effect on the battlefield. British defence sources have suggested that expanding Ukraine’s capacity to strike high-value targets deep inside Russian territory could increase pressure on Moscow to engage more seriously with peace negotiations.

A broader European pattern

Britain’s move is the latest in a series of steps by European allies to deepen Ukraine’s domestic defence capabilities rather than simply supplying finished military hardware. France has previously engaged in talks with Kyiv over establishing local assembly lines for the SCALP missile system, and other allies have similarly begun shifting from direct arms shipments toward technology transfer and joint production arrangements.

This shift reflects a broader strategic calculation among Ukraine’s Western backers: that a self-sufficient Ukrainian defence industry may prove more durable and less politically vulnerable than reliance on external supply lines, particularly as some allies — most notably the United States — have scaled back their contributions in recent months.

Whether the transfer of Storm Shadow blueprints translates into a meaningful battlefield advantage in the near term remains to be seen. Building the infrastructure needed for domestic missile production is a lengthy and complex undertaking, and experts caution it could be many months before Ukraine is capable of producing the weapons at scale.

Still, symbolically and strategically, the announcement marks a notable escalation in Western support for Kyiv — one that has already reshaped the tone of relations between London and Moscow, and one that is likely to remain a flashpoint in the weeks ahead as both sides weigh their next moves.