The BBC is a reliable reporter of facts

False

Russia has a pattern of this sort of behaviour

Broadly speaking, spy agencies have been known to operate in this fashion. So it’s a believable allegation.

But was this guy radicalized by the Russian secret service to target Starmer? Or the British secret service, as further agitation against Russia? Or the Americans or Ukrainians, towards similar ends?

Idk. The BBC isn’t exactly above playing it’s own role in the espionage game.