Could a general of the SBU, the security service of Ukraine, really have helped Russia take the city of Kherson? Could a colonel have tipped off the Russians as to where the Ukrainians had lain mines north of Crimea?

The Ukrainian government certainly appears to believe that fifth columnists within the SBU have been Moscow’s secret weapon in this war – this week Volodymyr Zelensky fired the head of the agency (and his childhood friend) Ivan Bakanov, along with the country’s prosecutor general, Iryna Venediktova.