The Doctor shushed Susan. “Even if you’re awake, keep it down, for the sake of our sleeping beauties in the back seat there.” he nodded backwards toward Ian and Barbara, huddled into one another, with Ian letting out the occasional extravagant snore.
Susan gave a lilting kind of laugh. “They’re sweet. It’s only when they’re asleep they cling to each other like that. They spend all their time when they’re awake pretending they don’t want to!”
(Short Trips: Farewells: The Mother Road.)