Few things cheer Britons more than the thought of Russian troops being turned to dust with the aid of British ingenuity. At the outbreak of the war in Ukraine, Boris Johnson toured the Belfast factory that churned out nlaws, the toddler-size rocket launchers that can whizz a 1.8kg warhead towards a Russian tank at 200 metres per second. It was no coincidence that one of Sir Keir Starmer’s first foreign-policy moves as prime minister was to wonder whether Ukraine should be allowed to fire “Storm Shadow” missiles 250km into Russia.