Doctor Who: 20 Things You Didn't Know About Heaven Sent
Some call Heaven Sent the best Doctor Who episode ever, but did you know these things about it?
On 28 November 2015, the penultimate episode of modern Doctor Who's ninth series was broadcast for the first time.
It saw the Twelfth Doctor, stricken by grief after the death of Clara Oswald, trapped alone in a mysterious castle while being chased by a strange, hooded creature called The Veil.
Using all his wits, the Doctor had to find the true purpose of his imprisonment and escape before The Veil destroyed him.
This episode was Heaven Sent.
Widely regarded as one of the best Doctor Who stories ever, Heaven Sent challenged the traditional formula of the show by giving almost all of its screen time to star Peter Capaldi. Capaldi did an amazing job carrying the story on his own, and more praise was given to the creature design, set design, and to Steven Moffat's writing.
When an episode is as beloved as this one - and when it's so different to everything else in the series - there are always behind-the-scenes stories and fascinating trivia attached to it.
And so, consider this list your own personal confession dial, full of secrets ready to be spilled! Although, hopefully, this one won't take four-and-a-half billion years to complete.
20. The Cycles Didn't Last As Long As You Think
It's difficult to gauge how long each version of the Doctor spends in the castle before the cycle resets and he does it all over again.
The Doctor says it'll take a day and a half to drag his dying body to the top of the tower, so that's one small indication of the time he spent there. But how long was he there in total?
Well, according to Moffat, the answer isn't as crazy as you might think:
"In my head the Doctor is in the castle for several weeks. I assume it varies, depending on how the rooms rearrange, but it's probably about three weeks."
If each cycle takes three weeks, and the Doctor is in the confession dial for 4.5 billion years overall... that's a frankly insane amount of resets required to break the wall.