After the expulsion of hundreds of embassy-based spies, the Kremlin is using riskier and less conventional methods, alarming spy chiefs across Europe. 

The head of MI5, Ken McCallum, said that Russian agents have been responsible for "arson, sabotage and more dangerous actions conducted with increasing recklessness" after the UK backed Ukraine in its war with Russia.

Guest: Mark Galeotti, Russia expert and director of Mayak Intelligence