Doctor Who Series 12: 10 Huge Questions After Fugitive Of The Judoon
7. What Is A Chameleon Arch?
The Doctor identifies the contraption hanging from the ceiling of Ruth’s TARDIS as a chameleon arch. An invention of the Time Lords, the arch is a way to hide a Time Lord’s true identity, even from themselves. It’s a drastic measure, rarely used, because with the headset on a Time Lord’s entire DNA is changed into that of another species. Their original biodata is saved and stored in a seemingly innocuous item such as a fob-watch, pendant or fire alarm button.
We have seen the arch used in the show twice before, with different effects. The Tenth Doctor had one in his TARDIS and used it to hide from the Family of Blood (Human Nature). The Master also has one in his TARDIS and used it to escape from the Time War by becoming a human baby (Utopia). John Smith kept the identical external appearance of the 10th Doctor, but he was fully human with just one heart and without the ability to regenerate, whereas the Master’s arch changed his entire physical appearance, de-aging him.
Ruth’s Chameleon Arch functions like the 10th Doctor’s. She still has her Doctor’s costume ready for when her original DNA is restored and it’s a perfect fit. Her childhood memories of growing up in the Lighthouse and moving to Gloucester in December 1999 are implanted like John Smith’s, but they are no less real to her. There can be no doubt that Ruth is an incarnation of the Doctor, unlike Jackson Lake whose fob-watch turned out to be just a regular time keeping device (The Next Doctor), the question is how does she fit in to the Doctor’s timeline.