The Doctor thinks he’s going to die, because he’s blowing up a spaceship while he’s still on it, with no chance of escape. Let me rephrase that: with no apparent chance of escape. He’s going to get out of it, it’s a prequel, dammit—but how? A consequence of River using up her regeneration cycle to save him in Let’s Kill Hitler, making him explosion-proof, justifying the line RTD (who, by the way, our hearts and wishes go out to in the light of his boyfriend’s illness) put in in The Sarah Jane Adventures: the Doctor stating that, oh, Time Lords can live forever? Or perhaps the TARDIS saves him, stubborn, sexy girl that she is. And, all questions aside, how does this connect to the Christmas Special itself, being set in England in 1941?
The important thing about this, though, that the Doctor calls Amy. On the TARDIS telephone, which, he knows she’s never going to pick up again; or at least not in time to save him. So why does he do it? He doesn’t call River, ’cause she’s in Stormcage, and perhaps because their time has come, their time is up—their First Night and their Last Night have happened; and perhaps she’s not supposed to help him this time. So why does he call Amy, just to talk, on a phone that she can’t even hear? He truly doesn’t believe he’s going to survive this. But he also doesn’t want to trouble her—he could call her properly, you know, phone her, on her phone, but he doesn’t. He left her and Rory behind, he gave them the life they deserved, he promised himself to keep them safe. He couldn’t possibly endanger them now, to save his hide, so he just pretends, just pretends, for a moment that he is, in fact, talking to her. He wants his last words to be “Merry Christmas, Amelia,” because she saved him, saved him when he came tumbling down towards Earth from a point so high in the sky, yet so low in his lifetime. Oh, Doctor, you are breaking my heart.