Doctor Who: The Aztecs (1964)

After the disappointment of The Keys Of Marinus, the BBC was playing to its strengths with its next story, a sumptuous historical costume drama: The Aztecs.

The TARDIS lands inside an Aztec tomb in 15th Century Mexico and Barbara is mistaken for the reincarnated spirit of the dead high priest Yetaxa.

The First Doctor, Ian and Susan are assumed to be her servants, but when Barbara learns of a human sacrifice to be made in her honour to summon rains to break the current drought she sees it as a chance to use her position to change the Aztec's ways.

The Doctor is horrified - stressing that "not one line" of history can be rewritten - but this doesn't stop Barbara from interceding in the sacrifice.

High Priest Tlotoxl (John Ringham, who hams his role up wonderfully, as though he is in a Grammar School production of Shakespeare, complete with sneering asides to the audience) starts to doubt Barbara's credentials as a minor deity and so begins a Machiavellian power struggle as various priests vie to prove or disprove her divinity, while The Doctor attempts to find a way back to The TARDIS (sealed behind a one-way secret door in the temple).

For those who thought The Doctor's love life was an invention of the Russell T Davies era, look no further than his wooing of Cameca (Margot Van de Burgh) in this story. The rogue spots her the moment he is led to the "Garden Of Rest" - for city residents over the age of 52 - and homes in on her so he can work his charms; the old dog!

However this charm rapidly turns to heartache when, having "accidentally" gotten engaged to Cameca, she realises that The Doctor will have to leave soon. He seems genuinely moved that he will be leaving her behind and even appears to consider taking her with him, but time is against them.

With Ian having convinced Barbara that she cannot change the mindset of a nation, the TARDIS crew direct all their efforts toward finding an escape before one or more of them become sacrifices to the gods.

How different things would have been if Cameca - as a potentail wife for The Doctor - had been allowed to travel away with the others...

Although not unpopular, the historical stories were gradually phased out of Doctor Who - the science-fiction stories were always the real ratings winners - to be replaced by the pseudo-historical tales which invariably feature some alien interference with Earth's history and The Doctor's efforts to ensure things stay on course and "not one line" of history is rewritten (well, give or take a few minor exceptions... he is The Doctor, after all).