In 1430 South America, Barbara is mistaken by the Aztecs as the reincarnation of the High Priest Yetaxa. Now regarded as a living deity, Barbara must decide whether or not to change history and end the Aztec practise of human sacrifice. But the high priest Tlotoxl schemes to disprove Barbara's divinity, threatening both Ian, who is to fight an Aztec warrior, and Susan, who has been chosen to wed a sacrificial victim. And how will the Doctor react to Barbara's decision?

On December 31st, 1963, BBC Chief of Programmes Donald Baverstock consented to a further ten episodes of Doctor Who beyond the twenty-six already agreed to. A month and a half later, on February 13th, 1964, the go-ahead was finally given for the entirety of the programme's fifty-two week season. Shortly thereafter, during the production of Marco Polo, story editor David Whitaker asked that serial's writer, John Lucarotti, to tackle another historical for later in the year, one which would mark the beginning of the newly-approved second half of Doctor Who's season.

Whereas Marco Polo had sprung from Lucarotti's research for a Canadian programme several years earlier, his ideas for his new adventure, The Aztecs, were inspired by his time spent living in Mexico. During his stay there, Lucarotti had become fascinated by the Aztec culture. In particular, he was astounded by the sharp contrasts inherent in that society, which had made enormous strides in astronomy, medicine and agriculture and yet forged no metal weapons or tools, was ignorant of the potential of the wheel, and practised human sacrifice. Lucarotti felt that the dying days of the Aztec civilisation, decimated by the forces led by Spanish explorer Hernando Cortes in 1521, would be the ideal setting for a more character-driven drama than Marco Polo had been. The Aztecs was commissioned on February 25th. As with his earlier scripts, Lucarotti wrote The Aztecs on his boat in Majorca, travelling to London to meet with Whitaker when necessary.

Shortly before The Aztecs was added to the schedule as Serial F, it had been agreed that each of the four regular Doctor Who castmembers would enjoy a two-week holiday during the remainder of the season. Consequently, Lucarotti was informed that Carole Ann Ford would be absent from the recording of the second and third episodes of The Aztecs. Whereas the preceding serial, The Keys Of Marinus, had dealt with William Hartnell's vacation by simply excluding the Doctor from two installments, it was agreed that Lucarotti should merely minimise Susan's appearances in the relevant episodes. This material could then be prefilmed prior to Ford's departure.

The director assigned to The Aztecs was John Crockett, who had earlier handled part four of Marco Polo; this would be Crockett's only other Doctor Who work. Two days of filming took place on April 13th and 14th at the Ealing Television Film Studios. On the first of these, Ford recorded two scenes, one of which would be inserted into each of the two middle episodes. The other day was used for filming the fight between Ian and Ixta, as well as the Perfect Victim's fall to his death. Part one, The Temple Of Evil, was then taped on Friday, May 1st, at Lime Grove Studio D; the remaining installments would, as usual, be recorded on succeeding Fridays.

Unusually, however, episodes two and three were taped not at Lime Grove but rather in Studio 3 at BBC Television Centre itself. For weeks, producer Verity Lambert had been battling to have Doctor Who shifted out of the aging Lime Grove studios and into more spacious and modern confines. On April 30th, John Mair of the BBC's Planning Department agreed that the programme should instead use Lime Grove Studio G and Studios 3 and 4 at the Television Centre whenever availability permitted it. Lambert, however, noted that the unusual long and narrow proportions of Studio G would make it impossible to achieve the sorts of vast sets that Doctor Who frequently demanded, and the debate would continue.

Unfortunately, the debut of Doctor Who in TC3 was marred when designer Barry Newbery discovered that the scenery for the base of the temple had been mistakenly broken up. Newbery hastily made use of whatever extra materials were at hand -- such as elements of Susan's cell, which had been needed only for the prefilming, and rented plants -- to create an impromptu “new” area of the Garden of Peace. The Aztecs then returned to Lime Grove Studio D for its concluding installment on May 22nd.

• Doctor Who: The Handbook: The First Doctor by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing, ISBN 0 426 20430 1.
• Doctor Who: The Sixties by David J Howe, Mark Stammers and Stephen James Walker (1992), Virgin Publishing, ISBN 1 85227 420 4.
• Doctor Who Magazine #266, 1st July 1998, “Archive: The Aztecs” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #7, 12th May 2004, “Do You Want To Know A Secret?” by Andrew Pixley, Panini Publishing Ltd.