Doctor Who series 9’s penultimate episode was a brain-melting hit, with Peter Capaldi’s Time Lord trapped alone in a shifting puzzle box of a castle with a terrifying monster and seemingly no escape. Towards the end of the episode, the truth of his predicament was revealed – he had been actually there for thousands (later billions) of years, reborn with new memories every few weeks to attempt the puzzle once again.


Eventually, the Doctor managed to escape after his respawning incarnations tunneled their way through harder-than-diamond rock over billions of years, and all rejoiced – but we were a little confused by what had happened as well.

If every room in the castle reset every so often, why didn’t the diamond wall do the same? Who left a set of dry clothes by the fire for the Doctor to find? And why was there an ancient picture of Jenna Coleman’s recently-deceased Clara hung on the wall?


Luckily for us (and the many people still arguing on the internet about this), Who supremo Steven Moffat has taken the time to answer some of these concerns in the latest issue of Doctor Who magazine – and the answers are pretty intriguing.

Take that diamond wall the Doctor punches through, for example – according to Moffat, there’s a very simple reason it doesn’t reset.


Could this have been even harder?

“It’s not a room in the castle, it’s the outer wall of the [Confession] Dial,” he explained. “The clue is that it’s 20 feet of Harder Than Diamond. Why bother making it so hard, if a resetting stone wall would do?”

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Fair enough – but there are still a few other confusing elements in this episode. Early in the story, the Doctor dives into a pond to escape the monstrous Veil, and finds an identical dry set of clothes for him to try on. But who put them there? Did the Time Lords happen to know his inseam, or did one respawn of the Doctor take off his clothes and just run around naked?

“Naked Doctor Who?? It’s AGAINST THE LAW, I tell you,” Moffat responded. “Showrunners have been executed for less. No, of course there wasn’t – I sort of wrote that moment to force you to think that the first time round the castle (the first of many times) wasn’t the same as the version we saw.”


The writer explained that in his mind, the first few times the Doctor went into that room he merely found a generic pair of clothes in his size and later changed back into his normal ones. But then once he didn’t make it back to them…

“Next time round, the Doctor finds his own clothes drying for him. The loop is complete – the end now triggers the beginning and that makes it permanent.”

As Moffat went on to lay out, this idea of the time loop getting “tighter” also explains a few other unexplained details in the episode, like the missing paving slab written on with chalk that told the Doctor where to find the diamond exit in room 12. Apparently (though Moffat emphasized that this was only his interpretation of the story), the clue was supposed to have been left by a previous version of the trapped Doctor looking for a shortcut…


“The first time round the castle, the Doctor is there for many years,” Moffat said, ”because there is no clue leading him to room 12. He’s ancient by the time he understands that room 12 is important.”

“After a few thousand years of this, he realizes he’s going too slowly. He needs to get the next version of himself into room 12 faster.”

His solution? Write ambiguous clues (“I am in 12”) all over the castle, hoping that some might survive the dodgy resetting process like the skulls in the lake, the drying clothes and the dust in the teleport room (as well as the portrait of Clara, which Moffat says the “soppy” Doctor painted himself). In the end the paving slab did make it through the reset, and the Doctor’s mission became a lot easier.


“The loop shrinks, the Doctor is younger as he punches the wall, and the Time Lords tremble as the storm grows closer,” Moffat concluded.

So there you have it – incredibly complicated answers for incredibly complicated questions. Classic Doctor Who.


To read more of this interview and more brand-new Doctor Who content, the latest issue of Doctor Who magazine is on sale now