Doctor Who: 20 Things You Didn't Know About Heaven Sent

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.