David Cartwright

David Cartwright is River's grandfather, a retired MI5 legend who once ran Berlin station during the Cold War and still carries himself with the quiet authority of a man who has seen real stakes. Now living out his days in a cluttered country house, he dispenses cryptic wisdom and watches his grandson's career with a mixture of pride and worry.

Pryce plays him as a man whose sharpness keeps flickering through the fog of old age, so you're never quite sure how much he's forgotten and how much he's choosing to withhold. That ambiguity gives every scene with him a low hum of tension — is this a doddering old man, or the smartest person in the room pretending otherwise?