The UK’s chief of the defence staff has slapped down Liz Truss’s suggestion that Britons could travel to Ukraine to take up arms in the war against Russia, saying doing so would be illegal. Sir Tony Radakin urged people not to rush towards “the sound of gunfire” and stressed there were many other ways that people in the UK could support those resisting the advancement of Vladimir Putin’s troops. The unusually direct comment will be viewed as a strict admonishment of the foreign secretary’s suggestion, which had already been rejected by the defence secretary, Ben Wallace. Last week, Truss was quizzed about the Ukrainian president, Volodymyr Zelenskiy’s call for anyone who wanted to “join the defence of security in Europe” to “stand shoulder to shoulder with Ukrainians against the invaders”. Asked whether Britons should venture out to fight, she said: “I do support that, and of course that is something that people can make their own decisions about. “The people of Ukraine are fighting for freedom and democracy not just for Ukraine, but for the whole of Europe because that’s what President Putin is challenging.” However, Radakin made clear his disdain at the intervention. He told the BBC’s Sunday Morning programme that any Britons who wanted to serve in the military should do so “in their own armed forces”. “We’ve been very clear that it’s unlawful as well as unhelpful for UK military and for the UK population to start going towards Ukraine in that sense,” Radakin said. “Support from the UK, support in whatever way you can. But this isn’t really something that you want to rush to, in terms of the sound of gunfire. This is about sensible support, based in the UK.” Asked about whether Truss was wrong to have suggested otherwise, Radakin said she was reflecting an understandable desire that Britons wanted to support the people of Ukraine in defending their lands from Russian troops. However, he said that sentiment should be properly “channelled into support for Ukraine”. “We’re saying, as professional military people, that is not necessarily the sensible thing to be doing,” he added. Wallace has also admonished the suggestion, saying that while defending Ukraine was a “just cause”, British citizens who wanted to fight should “come and join our armed forces”. He previously said: “There are people who will go … I think what I would say is unless you are properly trained, unless you are a, you know, experienced member of an armed forces, I think there are better ways for you to contribute to the security of Ukraine.”