Helen Jacobsen

Helen Jacobsen runs the Russia desk at MI6 alongside Carolyn Martens, and the two women have clearly been circling each other for decades. She is brisk, acid-tongued, and territorial about her patch, treating the hunt for a dangerous assassin as much a matter of professional pride as national security.

Zoë Wanamaker brings decades of stage-honed timing to a role built on institutional needling — every scene with Carolyn crackles with old rivalry dressed up as collegiality. The writing trusts her to convey a whole history of office politics in a raised eyebrow, which makes her a joy whenever she's on screen.