In a moment of pressure, he doesn’t hesitate to identify River as “an ex” and, later, she and we realise the depth of his feelings for her, the pain he suffers. “You’re always here to me,” he tells River. “And I always listen and I can always see you.” He opens his heart and for once seizes the chance to kiss her, even though she is now only “an echo”.

Alex Kingston and Matt Smith play these scenes with convincing tenderness.