Doctor Who: The Two Doctors (1985)

The Second Doctor is dispatched by the Time Lords (with Jamie McCrimmon) to investigate time travel experiments at Space Station Chimera in the Third Zone and gets entangled in a Sontaran attack on the station.

Meanwhile, The Sixth Doctor and Peri are relaxing, doing a spot of fishing when The Doctor has a 'funny turn'

Believing that an earlier incarnation is being killed, he decides to seek medical help from an old friend, the eminent geneticist Dastari (Laurence Payne), who dresses like he's in a Buggles video and happens to be in charge of Space Station Chimera.

Arriving there, The Doctor and Peri discover the place ransacked and deserted except for the corpses of the slain. Trying to deactivate the station's defensive computer system - which is trying to kill them - The Doctor and Peri stumble upon Jamie hiding out in the service ducts and claiming that "the Doctor has been killed".

The real mastermind behind the attack, Chessene (Jacqueline Pearce, sultry Servalan from Blake's 7) has left for Earth with one of the Sontarrans and her colleague Shockeye (John Stratton) as part of an elaborate plan to use The Second Doctor's genes to crack the secret of time travel.

Shockeye and Chessene are both Androgums, barbaric hedonistic humanoids, but Dastari has conducted numerous experiments on Chessene to overcome her natural instincts and boost her intelligence. He is now working with his protégé - and the Sontarans - to obtain the final key to unlocking time travel.

Following the trail of breadcrumbs, The Sixth Doctor, Peri and Jamie head to 1980's Spain to rescue The Second Doctor and put a stop to Chessene's plans.

From the story's great opening, starting in black and white and gradually fading to colour, with The Second Doctor - which must have wrong-footed its 1984 audience wonderfully - The Two Doctors quickly develops into a surprisingly intelligent conspiracy, especially as various parties try to double-cross each other further down the line.

Shockeye is a wonderfully grotesque creation of writer Robert Holmes, a chef driven by an overwhelming desire to sample as many and varied foods as he can lay his greasy hands on. The particularly clever touch is that, as an alien being, he regards humans as simply another 'dumb animal' ripe for butchery and sampling.

This strong element of the story attracted some criticism at the time (apparently from BBC Controller Michael Grade) for its 'cannibalistic' content - but, of course, anyone with a brain would realise that it's no more cannibalistic than a McDonald's advert for quarter pounders as Shockeye isn't human.

In fact the whole 'meat is murder' message is dolloped on with a trowel throughout the story and while the plot jumps slightly off the rails in the final half-hour when Dastari implants Androgum DNA into The Second Doctor (at Chessene's insistence, so she has a mate), the main problem with The Two Doctor's actually comes in the shape of the other aliens in the tale: the Sontarans.

Not only are the wasted as 'hired muscle' (although they talk about great plans and space fleets, we don't see any evidence of this) but they're simply wrong here: their heads look like bad Halloween masks with barely animate lips and not only are they considerably taller than most of the other humanoids in the story, but they're also noticeably different heights themselves - which is rather odd for a clone race of stumpy, potato-headed aliens (as seen in The Sontaran Experiment).

There are also some particularly violent moments in The Two Doctors, including one of the most shocking - and possibly gratuitous - murders of a minor supporting character. The Sixth Doctor kills one of the aliens with cyanide in a rather "unDoctorly" way as well.

Then, of course, there's the issue of where this all takes place in The Second Doctor's timeline, as he's freely talking with Jamie about The Time Lords - but the Time Lords aren't revealed to Jamie (or the audience) until The Second Doctor's last story, The War Games.

Canny fans have devised the Season 6B theory to get around this - which is wholly acceptable in a series based around time travel!

But for all these comparatively minor issues and the pointless location shooting in Spain (so producer John Nathan-Turner could have a holiday in the sun), The Two Doctors is a far better story than it possibly should have been because of Holmes' crafty script and the central performances of the two Doctors (Patrick Troughton's third and final return to the role), their traveling companions, Dastari and the two Androgums.

And, as a special Christmas treat to all my fellow Periphiles (and celebrate the fact that I have now reviewed all of Colin Baker's episodes as The Sixth Doctor), I leave you with reminder of another reason why this is such a stand-out story...