British prime ministers seldom arrive in foreign capitals enduring daily ballistic missile attacks. Andy Burnham was in Kyiv yesterday, celebrating Ukraine’s 35th anniversary of independence, barely four days after Russian cruise and hypersonic missiles had killed at least 16 people in the city.

A shortage of interceptors means that Ukraine struggles to defend itself against these brutal raids. So it was right that Mr Burnham should have chosen Kyiv for his first overseas visit as Prime Minister and, to his credit, he brought more than simple solidarity for Ukraine’s heroic people.

Now that Volodymyr Zelensky has precious few defensive systems capable of destroying incoming Russian missiles, his most effective response is to strike back against their factories, storage bunkers and launch facilities. Ukraine is using armed drones for this purpose, but they cannot seriously damage hardened or underground facilities.

For that task, Ukraine needs missiles with specially designed warheads. Hence Mr Burnham gave Mr Zelensky the blueprints for Storm Shadow cruise missiles, an Anglo-French weapon which the two countries have been supplying to Ukraine since 2023. When it comes to warding off Vladimir Putin’s missile offensive, Ukraine’s best – and, for now, only – form of defence is to destroy these weapons in their silos and degrade Russia’s capacity to produce them in the first place.

Mr Burnham’s decision to give Ukraine the plans for Storm Shadow – and his earlier approval for Mr Zelensky to use British-made drones to strike targets inside Russia – are welcome signs that Britain will not waver from standing firm against Putin’s aggression. Neither should the Prime Minister be intimidated by the Kremlin’s outpouring of threats nor be perturbed by the fact that Andrei Kelin, the former Russian ambassador, has left London without any successor being announced.

For years, the sole function of Russia’s embassy in Kensington Palace Gardens has been to issue blustering statements packed with lies and menace. Even its intelligence station was cleared out after the Salisbury poisonings in 2018 when Britain expelled 23 Russian spies. What was Mr Kelin doing all day? Mr Burnham should allow nothing to deter him from aiding Ukraine’s righteous defence. As our report today on Kyiv’s assistance with Britain’s own defence indicates, our national security depends upon it.