In Heaven Sent,

the Doctor uses the positions of the stars to determine that he's been in a loop for over 7,000 years, and we then see the loop continue for over two billion years.

My question is, how did he come to this conclusion the first time around? In other words,

what happened 7,000 years ago, the first time he entered the castle, before there was any visible passage of time to enable him to deduce that he was about to become part of a 2,000,000,000-year-long cycle?

  • 4
    You're quite right, he had to work on fewer clues to figure out what to do. Good question.
    – Mr Lister
    Commented Nov 29, 2015 at 8:35

1 Answer 1


On his first entry to the castle, he’s missing two clues:

  • The word “BIRD” scribbled in the sand of the teleporter room
  • The passage of the stars

So we need to work out a course of action without either clue, the latter of which will only become apparent in decades to come.

By the time we arrive in the diamond room, here’s what we know:

  • The Veil is temporarily slowed by confessions, and these confessions drive the layout of the castle.
  • The clues are supposed to lead the Doctor to Room 12; to the insurmountable wall of diamond.
  • All the rooms in the castle reset to just before the Doctor’s arrival.
  • The Doctor knows more about the Hybrid than he’s letting on.

It’s not a stretch to suppose the point of this castle is to get information about the Hybrid. Continue backing the Doctor into corners, he confesses to buy a bit more time, and eventually you learn what you need to know, right?

The two previous dead ends have resulted in confessions, but clearly they’ve been unsatisfactory to the powers-that-be. The Doctor works out how this is supposed to go: trapped with no way out, facing down the Veil, he gives up information about the Hybrid. His life is spared, and somebody has their secret.

(Note: if the Doctor sells out, he’d die anyway. This is standard villain behaviour.)

He also works out that there’s something beyond the wall. If he can get through it, there’s an alternative exit route.

There’s enough here to work out what needs to happen next. Chip away at the wall, over thousands of copies, and eventually you’ll get through. (He doesn’t know if this will work, but he’s running out of options.)

The word “BIRD” is a nudge in this direction. He’ll work it out faster on subsequent iterations – perhaps earning him an extra punch or two – but it’s not absolutely necessary to work it out. The passage of the stars is a similarly useful but not necessary clue.

  • 5
    On the first go he's also missing the pile of skulls, and his dry clothes. Commented Nov 29, 2015 at 12:04
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    “He doesn’t know if this will work, but he’s running out of options.” Yeah: I think the very first time he gets to the superdiamond wall, he knows he was teleported here, and he has a good idea about the workings of the teleporter technology, so he might think well, there’s a chance I can re-materialise myself even if I die. But he doesn’t know that — he basically just refuses to give up the secret of the hybrid. So f— you, Time Lords (or whoever put him in there). Man, the more I think about this episode, the more I love it. Commented Nov 29, 2015 at 12:22
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    @DanielRoseman: oh lord. Yes. So the first time, he spends a good portion of the loop running around naked. Commented Nov 29, 2015 at 12:23
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    Since we didn't see them in the scene where the Doctor changes out of his wet clothes, presumably he kept his question-mark themed underpants on the first time.
    – Nathan K.
    Commented Nov 29, 2015 at 14:55
  • 3
    You assume he finds the wall the first time. I'm not convinced. All we know for certain is that every single iteration (except the last) he is killed by the veil, that he does figure out that the transporter has a copy of him, and that he activates it. There could be hundreds of thousands of variations of events that slowly settle into the stable loop we see 7000 years later, each one leaving more a and more clues for the next Doctor. Commented Dec 1, 2015 at 6:21

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