For all that’s wrong with the sixth Doctor’s TV episodes, there are hints of what might have been – and the shape of things to come. The veiled left-wing politics of Vengeance on Varos and The Mark of The Rani are buried deep in the mix, but they’re still more pointed than anything else since about 1977, and begin a rich seam of anti-establishment subversion that was better mined by Andrew Cartmel’s writers. And The Trial of a Time Lord – with a Doctor who deliberately decides to investigate the mystery of Ravolox, put an end to the gun-running on Thoros Beta and answer the Hyperion III’s distress call – means that the segue to the interventionist seventh Doctor is less sudden than it might have been.

And then there’s Colin Baker, as distinct from the sixth Doctor. On TV, the sixth Doctor was born out of the failed fifth. Season 21 shows us a story arc in which the fifth Doctor’s continuing inability to find peaceful solutions in a violent universe ultimately means he turns his back on even trying to solve the problems of Androzani. The sixth Doctor claims his previous incarnation was becoming neurotic, and effete – in the sense of being worn out and no longer capable of effective action. The sixth Doctor is therefore presented as the solution: a new Doctor, bursting with vitality, ready to face up to this brutal universe and sort it out. The costume, the bullish persona, everything adds up to this conclusion.

In itself, this has the seeds of something quite compelling, even if it does rely on thoroughly trashing the previous incarnation. However, in practice the production office doesn’t pull it off. Rather than having the sixth Doctor being proactive – seeking out injustice and diving into danger – we get another set of stories that set the Doctor up as ineffectual, unless he’s carrying a gun. In Attack of the Cybermen he’s constantly one step behind Lytton. While his successor would have deliberately landed on Varos to put a stop to its horrors, the sixth only goes there to refuel (after a petulant row with Peri). It’s not even that he’s particularly violent: the acid bath deaths in Varos are set up as accidents, although the premeditated killings of Quillam, the Chief of Operations, Shockeye and the Borad (and the Doctor’s amused quips) are rather more questionable. It’s that he’s as much a victim of circumstance as he accuses his predecessor of being. By the end of the season, he’s actually relying on the Daleks to sort out the problems on Necros. He’s become effete in the other sense – self-indulgent, affected and lacking in character.

While The Trial of a Time Lord corrects some of this, we’re still left with a Doctor who is a slave to events, manipulated by his own future self, set up as a stooge by the Time Lords and rescued by the Master because he’s an easy mark. Even his new companion seems to see him as a fat clown to be pitied. No wonder Andrew Cartmel wanted to restore some dignity to the character.

As did Colin Baker. There’s a great episode of The West Wing where Toby says that there are two Bartlets: “Dr. Jekyll and Uncle Fluffy”. Equally, you could argue there are “the sixth Doctor and Uncle Sixie”. In Season 22 we mostly got the sixth Doctor – a pompous but ineffectual bully in a clown’s outfit. The one exception to that is The Mark of The Rani where, for the first time, we meet Uncle Sixie. Uncle Sixie is an avuncular raconteur, with a wistful and romantic view of the universe, and a burning disdain of unfairness and hypocrisy. We get hints of this character in the “nevermore a butterfly” speech in The Two Doctors, and in the debate with the Inner Voice in Slipback, and then The Trial of a Time Lord suddenly features a Doctor who’s snuggling up to Peri under an umbrella and being bossed about by Mel.

But it’s really thanks to Big Finish that Uncle Sixie has become so established. Early on – before they secured the services of Paul McGann and then Tom Baker – Colin Baker was Big Finish’s favourite child. Quite rightly – given Davison nailed it on TV and the seventh Doctor already had a long literary afterlife. In the first two years of Big Finish, Colin Baker got all the big breaks – the first audio-only companion (one deliberately conceived as a foil to Uncle Sixie) in The Marian Conspiracy, the first Brigadier story The Spectre of Lanyon Moor, and Big Finish’s first classic The Holy Terror. Colin Baker and Big Finish very carefully made sure all of these plays featured Uncle Sixie – the safe, avuncular, cuddly version of the Doctor rather than the brash, arrogant Season 22 model. Over the last decade we’ve learned to accept this as the sixth Doctor. And why not – it’s certainly a more comfortable interpretation than the original.

As for the Valeyard: a Doctor driven mad by his impending final death? Retrospectively, there are hints of this in the sixth Doctor’s existential angst at the thought of his paradoxical death in The Two Doctors, and his horror at discovering his own grave in Revelation of the Daleks – both of which suggest that possibly Holmes and Saward had brainstormed the idea of a dark future early in 1985. A couple of novels (Millennial Rites and Matrix), and the Unbound audio He Jests at Scars have explored the character to some extent, although none has really nailed Holmes’ conception of a thirteenth Doctor at the end of his life, staring into the abyss and realising that he could have done so much more, if only he had more time. This, perhaps, makes Colin Baker himself the closest thing we have – the only Doctor who’s really had the chance to go back and extend his life, correct the mistakes of the past, and hijack the remainder of the sixth Doctor’s existence for his own ends…

Meanwhile, back in 1987 the production office hadn’t given up on the idea of a Doctor actively crusading against the forces of evil. Although the execution had been botched the first time around, the concept of a character who tried not to dirty his hands with rough and tumble violence, but who retained a steely determination to put a final end to tyranny and corruption was too good to forget. Though the McCoy years are frequently presented as a break with the immediate past, many of these themes are going to re-emerge during Seasons 24-26, and perhaps be taken further than either John Nathan-Turner or Eric Saward had originally conceived.

I’ve put it off long enough. The Doctor is back. The Rani is waiting.

Their destiny is now…