So many theories were bandied about as to the identity of the Doctor's wife. How wonderful that the answer turns out to be the most elegant and, perhaps, most obvious.
The Time Lord has been wedded to his Tardis pretty much from day one. In the earliest days of Doctor Who, the ship was depicted as an almost sentient force that could influence the lives of its occupants. It wasn't until third Doctor Jon Pertwee's day that she gained her femininity.
In his debut story, Spearhead from Space, he told the Brigadier, "Oh, there she is. How nice of you to look after her for me." Four years later, in The Time Warrior, he patted the police box and said, "Well done, old girl. Absolutely on target… For once!"
From then on, "old girl" would crop up regularly as he fondled and thumped the hexagonal central console. The 11th Doctor even calls her "dear". For hundreds of years they've been inseparable, touring all time and space together. The Tardis is indeed the Doctor's partner for life.
And now, momentarily, "she" has been embodied in a beautiful woman that he can converse with, touch and adore. Move over, Rose Tyler et al. At last - in powerhouse performances from Matt Smith and Suranne Jones - we see the love of the Doctor's life. For me, that is the magic of this episode.
I must admit, as the story was getting under way, I really wasn't sure I was going to enjoy it. The grungy setting, wacko characters and peculiar dialogue were alienating, maybe stylised after those 1990s French fantasies by Jeunet & Caro (Delicatessen and The City of Lost Children). Then, suddenly, I was captivated.
Yes, there were fan-pleasing elements: the white cube Time Lord distress signal, seen only once before, way back in The War Games (1969). The spaceship graveyard and mish-mashed bodies were a steal from The Brain of Morbius (1976). The Celestial Toymaker (1966) and The Mind Robber (1968) both showed the Tardis lured beyond the normal universe and the Doctor's companions tormented by a malign intelligence.
How delightful to see so much more of the Tardis interior with its preponderance of roundels and hexagons. Other than a glimpse of wardrobe in The Christmas Invasion, this pleasure has been denied us since Who returned in 2005.
Many young fans were surely thrilled to revisit the domed Christopher Eccleston/David Tennant control room, but how many fan-farts like me were holding out for the classic white version, even the wood-panelled study discovered by Sarah Jane Smith in 1976?
But despite these nods to the past, I kept thinking, "Doctor Who has never been like this before" and "What the hell is going to happen next?" Prize-winning fantasy writer Neil Gaiman's first stab at the series delivers an instant oddball classic that is both breathtakingly novel but as old as the programme itself.
The secret of The Doctor's Wife is way out there - and always has been.