Doctor Who: 20 Things You Didn't Know About Heaven Sent
1. Moffat Knew The Cliffhanger WELL In Advance
Some of Steven Moffat's story arcs felt made up on the fly, but the man had impeccable planning skills when it came to Heaven Sent.
In an interview with Doctor Who magazine in June 2014, the writer hinted at a whopper of a cliffhanger coming up. That cliffhanger would eventually be Heaven Sent's - which was broadcast almost 18 months after this interview - where the Doctor returns to Gallifrey.
In other words, Moffat had figured out how Heaven Sent was going to end while he was still working on Series 8. That's how far in advance this man's mind works sometimes. Very impressive!