Even the most devoted of Doctor Who fans – those who deal with timey-wimey complexity on a weekly basis – can occasionally be left confused by one of Steven Moffat's plot-lines.
The most recent one to have fans scratching their heads, however, is just how Matt Smith's eleventh Doctor could have prevented his death in Christmas special The Time Of The Doctor when viewers clearly saw his grave in the series seven finale The Name Of The Doctor.
Well, after being asked that very question in the latest issue of Doctor Who Magazine, Moffat decided to clear it up - with a little help from a friend.
“I’ve often wondered about that," he writes. "Fortunately, late one night, the Doctor turned up in person and explained it to me:"
"THE DOCTOR: Changing time is tricky. It’s a bit like a detective story: so as long there isn’t an actual body, you’ve got a certain amount of wiggle room – for instance, if the body has, rather conveniently, been burned on a boat in Utah. Here’s the thing: I can change the future so long as the future has not already been established as part of my own past. I can’t rescue Amy and Rory because I already know that I didn’t."
“But what do I know about Trenzalore? There’s a big monument that looks very like my Tardis. There’s a temporal fissure leading to my timeline. Maybe it’s my grave. Maybe, one day, it’s my burial ground. Maybe it is something else entirely, and we got it all wrong. Don’t know. Don’t plan to find out for as long as possible. The main thing is, Clara still jumped into my time stream, and ended up helping me through all of my life. All that is established, unchanged – but there’s wiggle room!”
So, that's that cleared up then… Thanks, Doctor!
For more from Steven Moffat and an exclusive interview with eighth Doctor Paul Mcgann, Doctor Who Magazine is out now.