Kate Stewart

Kate Stewart runs UNIT with a scientist's mind rather than a soldier's instinct, and she says as much the moment the Doctor questions her methods. Composed, precise, and unflappable in the face of alien incursions, she treats the extraordinary as a matter of protocol, always weighing evidence before reaching for a weapon.

Redgrave gives her a dry, unhurried authority that never needs to shout to be obeyed, which makes her a rarity among UNIT commanders. The writing lets her be the Doctor's equal rather than his subordinate, someone who pushes back on him with facts instead of deference, and that friction is what makes her scenes crackle.