The lessons military planners are learning from the Ukraine invasion and what it means if the UK went to war with Russia

Prof Clarke, former director of the RUSI and a fellow of Kings College London, told Sky News: "With British military planners … the idea of having to go all-out to fight a proper big war was 'we'll only do it with the US and certainly won't be doing it for, let's say, the next 10 years'. "24 February showed that… Russia is now a manifest threat and will be for as long as Putin is in power and probably his successor as well. It is THE problem of European stability and security."