When you are a time traveller, there is one place in all of space and time you must never go... Trenzalore.
15 minutes into this season finale, promised by Steven Moffat and co to be a game-changer for the show, it emerged that this location of the Doctor's grave, "potentially the most dangerous place in the universe", was exactly where he had to go, crossing his own time line to do so. No wonder the Tardis threw a hissy fit.
The Doctor and Clara were forced to go on a journey, unusual even by their standards
It transpired the Tardis had the right idea. No sooner had the Timelord and his pals - Clara in visible form, River Song lending an ethereal helping hand - rocked up in this unforgiving place, than those villains straight from Doctor Who's central casting cupboard, the Whisper Men with their waxed-down faces and bowler hats, were heralding the arrival of our Timelord's Nemesis, the Great Intelligence.
The inevitable almighty battle led to the Doctor's disappearance, stopping only for a heart-rending chat, and kiss, with River Song - how DOES she manage to maintain her chemistry with whichever Doctor's incarnation she has to deal with?
Jenna-Louise Coleman was on fine form as the 'Impossible Girl', taxed with saving her confusing companion - and hopefully with the help - 'mentally linked' - of the all-knowing River Song.
But the real treats for for longtime fans were those elliptical glimpses of the Doctor's ghosts - in every different form, Messrs Hartnell through to Tennant (naughty Colin Baker, swearing he wasn't part of the 50th anniversary) even that of the oft-elusive Christopher Eccleston (was that REALLY them all? Cross fingers there were no extras in coats) - all the way to a tantalising... John Hurt???... to keep us on our toes for the 50th anniversary show on 23 November, as we were told with a trumpet at the end of the episode.
And nearly as moving as the Doctor's being faced with his own grave, and that of River Song, was the ghost of Tardis future, dying from the inside out. If ever there was an occasion to feel affectionate towards something everyday and inanimate, this was it.
How satisfying was this finale for all true fans? Let us know...