Ingrid Tearney

Ingrid Tearney runs MI5 from the top floor, First Desk in all but name, gliding through Whitehall corridors with the ease of someone who has never had to raise her voice to get what she wants. She treats Slough House and its washed-up agents as an inconvenience beneath her attention, until circumstances force otherwise.

Sophie Okonedo plays power as something worn lightly, all charm and composure, which makes Tearney more unsettling than any shouting spymaster could be. The writing lets her seem reasonable in every scene, and that reasonableness is precisely the point — you're never quite sure whose interests she's actually serving.