In this final episode, we have the first ever interview with serving MI5 officers who work in counter intelligence.Tom and Kate talk about the challenge of grey zone threats from Russia and reveal their shock at the Salisbury spy poisonings.They also reveal that the Security Service has bolstered protection for people in the UK deemed at risk from Russia and is doing “everything we can” to prevent another Salisbury-style attack, but there are no “absolute guarantees” – in the grey zone.Guests:Tom, senior MI5 intelligence officer working on RussiaKate, MI5 intelligence officer investigating the activities of Russia’s military intelligence agency, the GRULord Mark Sedwill, former UK national security adviserDominic Grieve, former senior Conservative MP, former chair of Parliament’s Intelligence and Security Committee, former attorney generalCredits:Written and narrated by Deborah Haynes Edited and produced by Chris ScottProduction support from Sophia McBide and Michael GreenfieldThe Head of Sky News Radio is Dave Terris