I have a vague memory of the Doctor inputting code in one form or another to the Tardis, to control its appearance. I have recently re-watched Logopolis (online), and there doesn't appear to be any actual 'code' or language on-screen before the pyramid and Tardis graphics appear.

Are there any other classic episodes where the Doctor shows on a screen the use of maths / programming to alter the Tardis? My recollection is possibly hex code on a pink or orange background.

2 Answers 2


Firstly, it's worth noting that, for 99.9% of the show's run, the TARDIS' appearance hasn't been controllable at all - its chameleon circuit is broken, locking it into its iconic "police box" form. Logopolis is one of only two episodes in which the Doctor attempts to fix the chameleon circuit - as of the reboot, he's decided he likes it as it is.

The only other episode in which the chameleon circuit is repaired is Attack of the Cybermen, where the Doctor explains that the TARDIS automatically disguises itself, and he has no control over what it chooses to disguise itself as. Indeed, the first time the TARDIS transforms, the Doctor is outside the TARDIS watching it happen:

Peri: I thought you said it was going to blend into its surroundings.

Doctor: Oh, she's probably thinking about it. Come on, let's find out where those signals are coming from.

[the TARDIS changes into a highly ornamented dresser]

Peri: Oh, neat, Doctor. Very neat.

Doctor: Neat?

Peri: Very neat. I mean, there's nothing at all incongruous about that.

Doctor: Well, she hasn't done it for a long time. She's out of practice.

(from the transcript here)

So I'm afraid your vague memory is incorrect: the Doctor cannot control the TARDIS' external appearance by any means.

  • At the end of Clara's run as Capaldi's companion they stole a second TARDIS and that one had a functioning chameleon circuit, which allowed it to disguise itself as a diner. One has to suspect that possibly had some input from its crew as it was important to their plan. TARDISs are, after all, sentient and telepathic. Commented Nov 26, 2022 at 6:54
  • Also, IIRC, the TARDIS has a psychic ability to cause anyone who sees it to think it looks "normal", so even if, say, an ancient Roman sees it in the form of a police box, they don't think there's anything odd about it. But that's not all that consistent. Commented Nov 27, 2022 at 1:21

This was addressed in Meanwhile in the TARDIS #1, a minisode from series five set moments after the end of The Eleventh Hour. It was included as a special feature on the DVD release, but is also on Youtube:

On brief, the TARDIS automatically analyses its surrounding (in twelve dimensions, no less) and determines the best outer shell.

Amy: Why is it a police box?

[Amy babbles a bit; I'll spare you]

Doctor: Well it's not really a police box. Which, by the way, is a special kind of telephone box that policemen used to use.

[More babbling]

Doctor: It's camouflage. It's disguised as a police telephone box from 1963. Every time the TARDIS materializes in a new location, within the first nanosecond of landing, it analyzes its surroundings, calculates a twelve-dimensional data map of everything within a thousand mile radius, and determines which outer shell would blend in best with the environment. And then it disguises itself as a police telephone box from 1963.

Doctor Who Minisode "Meanwhile in the TARDIS #1"

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