Okay. In The Time of the Doctor, Clara jumped on to the dematerializing TARDIS, so the TARDIS extended its force field to save Clara from the Time Vortex. So, it needed to run at slow pace (or time pace, whatever) just to reach Trenzalore 300 years late.

But why didn't the TARDIS simply open the door, let Clara in and run at normal pace? Last I remembered, she was holding the doors.

  • Off the top of my head (and with no Canon backup), I'd say Clara never tried to open it while hanging on (probably due to being terrified.) The Tardis is more than a box; it's a living, sentient entity. The key doesn't open the door; the Tardis does, when it recognizes a valid request. A legitimate key (the Doctor's or someone else, as when we see they retrieve one to use on Gallifrey) counts as one. The doctor snapping his fingers counts as another. Even picking the lock can work, although I wonder if it will only work for someone otherwise 'authorized' to be in there. (E.g. Adric.)
    – K-H-W
    Jan 9, 2015 at 2:35
  • @K-H-W TARDIS was actively saving Clara (unlike Captain Jack Harkness who died trying the same) and it was running late. Why couldn't it simply open the door even without the request? Ofcourse, nobody would like flying Time Vortex hanging on the door.
    – user931
    Jan 9, 2015 at 2:45
  • Honestly, my guess is simple.. It's both a living, sentient being.. AND a machine. It extended it's force field because that option/judgement call was within it's operating parameters... But it only opens the door in response to a valid request... Had Clara tried her Key, or even Snapped her fingers, it could have responded.. But as a hybrid of Machine and Sentient being, it was doing exercising judgment where it could (extending the field), and waiting for a signal for what it had hard-coded logic to handle (the door.)
    – K-H-W
    Jan 9, 2015 at 2:52
  • @K-H-W But, TARDIS doors automatically opened in The Day of The Doctor when Clara drove her bike into it.
    – user931
    Jan 9, 2015 at 2:56
  • 4
    The Doctor gave Clara his sonic screwdriver and told her to plug it in the console. This sounds like some sort of Emergency Program A (or whatever...first seen in Ninth Doctor's "Bad Wolf"), in which the TARDIS must take the companion home. Pure speculation: The TARDIS was carrying on the command, but had to extend the field and slow down when it noticed Clara was still hanging outside. It couldn't let her in because it's against Emergency Program A.
    – tilley31
    Jan 9, 2015 at 4:03

1 Answer 1


It's been established that opening the TARDIS doors while time-travelling has unpleasant and unpredictable consequences. This happens in a First Doctor story, Planet of Giants, and causes the TARDIS crew to live the plot of Honey, I Shrunk the Kids.

It happens again (on purpose this time) in the Second Doctor story The Enemy of the World where it causes decompression so strong that the TARDIS crew are nearly sucked out. This actually happens to the main baddie, and the Doctor describes his fate as "unpleasant".

Similarly, it appears to be impossible for the TARDIS to dematerialize with the doors open; in "The Husbands of River Song", the Doctor says (emphasis mine):

DOctor: Maybe the engines are interfering with themselves. Wild theory, but what if this machine had certain safeguards. For instance, maybe it can't take off when a life form registers as being both inside and outside at the same time?

River: Head and body.

Doctor: Which would mean, and again, I'm just, I'm just wildly theorising here, that the door would not engage properly.

River: Of course. It can't seal the real-time envelope.

Doctor Who Christmas 2015: "The Husbands of River Song"

Although not explicitly stated in the episode, presumably the doors also do not engage (and thus the TARDIS can't take off) when the doors are open.

So the only way the TARDIS would have been able to let Clara in would be to first stop de-materializing. The show never explains why he doesn't do this, although personally I like tilley31's answer in the question comments: the TARDIS was running an emergency program, and the Doctor's instructions overrode everything else.

It's also possible that this was a safety feature of TARDISes: you can't abort a de-materialization once it's begun, or once it's de-materialized a certain amount. We have no evidence to support that, but it's a fair guess.

  • There have been a couple of episodes where the TARDIS has traveled with the doors open. In The Runaway Bride, 10 flies the TARDIS along a highway with the doors open while coaxing Donna to jump out of her kidnapper's taxi. There was another with Clara (I think) sitting on the edge of the entrance to the TARDIS with both doors open, looking out into space. So it's entirely possible for the TARDIS to move (in the Earth's atmosphere and in space) with the doors open.
    – FreeMan
    Jul 22, 2021 at 13:26

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