He hesitates with one hand on the latch, the other caressing the stable door itself, which has been worn smooth and silver by sun and weather. At the back of the building, he knows, his past self waits, still heavy with guilt. For a moment he's seized by the urge to drop the latch and walk around the stable and tell the man he once was that it's all right (or will be)--those children have finally been saved and so he can finally bear to go in to see this child. He doesn't have to hate himself anymore, or hold his name as less than truth.
But he's already here, in this time, too often for safety (in a distant court with some well-dressed astronomers; many times in a sheep field; outside a stable much like any other, except that time is set here so firmly that it stands about the place like unseeable light), so instead he takes the latch and lifts it, and opens the door and looks inside.
"Hullo," he says. "I'm the Doctor." And at long, long last it is no lie.
eta: And here is better story than mine.