The Doctor, Susan, Ian and Barbara find themselves on Earth in the middle of the twenty-second century... and the Daleks have invaded. Now the streets of London are stalked by the Daleks' brainwashed human puppets -- the Robomen -- while more terrible monsters roam the countryside. Ian stows away aboard a Dalek saucer, while the others forge an uneasy alliance with a desperate band of freedom fighters, led by the scientist Dortmun. But in order to reclaim the planet for humankind, they must first uncover the true purpose of the Daleks' massive mining operations in Bedfordshire.

Even before their first serial had ended, the Daleks had become a phenomenon, propelling Doctor Who's ratings to an increase of nearly two-thirds. As such, the production team asked the monsters' creator, Terry Nation, to stop work on an historical tale, “The Red Fort”, and instead write the science-fiction adventure The Keys Of Marinus at short notice. By the end of February 1964, less than a month after the broadcast of the final episode of The Daleks, plans for a sequel were already afoot. Nation had agreed to a narrative in which the Daleks invaded Earth, and this was provisionally scheduled to be the final serial of the programme's original recording block. On March 17th, Nation was commissioned to write “The Daleks”, which shortly thereafter was retitled “The Return Of The Daleks” and then “The Invaders”.

As the end of the shooting schedule neared, producer Verity Lambert and story editor David Whitaker started finalising plans for Doctor Who's future. It was already decided that there would be a break in transmission following The Reign Of Terror, meaning that “The Invaders” would be the second story of the programme's second season. Lambert and Whitaker were particularly concerned about the composition of their regular cast, and considered -- but eventually rejected -- writing out Barbara in order to reduce the cast size.

Carole Ann Ford felt that Susan was not being properly developed as a character

Meanwhile, Carole Ann Ford had grown unhappy on Doctor Who. She felt that Susan was not being properly developed as a character, and nothing had been done with her own suggestions, such as having Susan develop a crush on Ian. Ford's husband -- who was acting as her agent -- had unsuccessfully attempted to negotiate a premature release from her contract. On March 12th, the press reported that Ford was indeed leaving Doctor Who when her obligations were fulfilled at the end of the first recording block. With this in mind, Lambert and Whitaker decided to replace Susan with another teenaged girl; the change would occur at the end of “The Invaders”. On July 30th, an exit scenario for Susan was written, which Nation then incorporated into his script for episode six.

Even as Nation's work on “The Invaders” was progressing, Lambert was making little headway in her efforts to secure a second production block for Doctor Who. By the middle of August, the Controller of Programmes for BBC One, Donald Baverstock, had granted Lambert only an extra four-part serial to be made after the Dalek story. However, Lambert was unwilling to eliminate Susan from Doctor Who if the series was to end a month later. As a result, she urgently needed a firm decision from Baverstock. If further episodes were authorised, the new companion would have to be hurriedly cast. If Doctor Who was to end with the additional four-part serial, Lambert would have to commission a suitable set of scripts, amend her stars' contracts, and ensure that the end of “The Invaders” was rewritten appropriately. Finally, on August 14th, Baverstock agreed to a thirteen-week extension beyond the Dalek sequel.

By this time, Nation's scripts included a teenaged rebel called Saida, an English girl of Indian descent who, after Dortmun's death, was revealed to be his daughter. Saida stowed away aboard the TARDIS at the conclusion of “The Invaders”, becoming the new companion. Subsequently, this character evolved into a white character named Jenny. Other changes made during the writing process included David's surname evolving from Somheim or Sonheim to Archer. Baker was originally named Roger Krish, while Larry Madison's first name had been Robbie.

The story's setting was shifted from the twenty-first century to the twenty-second, which required deleting references to 1980 as the year of the initial Dalek attack. The Robomen were conceived as wearing only a small disc on their temple, with wires snaking into their hair. Instead of crocodiles, David and Susan were menaced by mutated humans in the sewers. Wells' role was originally much smaller: he was freed from the Dalek shuttle by Ian and left to tend to other escapees. Three old women lived in the shanty in the woods, rather than the degenerate mother and daughter. The final episode saw the Daleks attempt to kill all their slaves by trapping them in the mines, which would be deluged with lava when the bombs exploded.

With Jenny no longer joining the TARDIS crew, another actress would be found to replace Pamela Franklin

On August 17th, Lambert selected Pamela Franklin to play Jenny, and asked that she be issued a contract for nineteen episodes. At the same time, however, she learned that William Hartnell, William Russell and Jacqueline Hill were all unhappy with the new contracts tendered for the additional episodes, placing the future of Doctor Who in doubt. On the 19th, Lambert elected to proceed with the elimination of Susan from the series in “The Invaders”, but asked Nation to reduce Jenny's prominence in the scripts, as the character was no longer going to join the TARDIS crew. This meant that another actress would be found to replace Franklin; she would go on to acclaim in films such as The Prime Of Miss Jean Brodie and The Legend Of Hill House. Lambert was ultimately successful in re-signing her three remaining stars, in part thanks to Baverstock's guarantee, obtained by August 21st, of another thirteen Doctor Who episodes. As such, it was decided that Susan's replacement would be introduced in the serial following “The Invaders”, which became The Rescue.

All four of the Dalek casings constructed for The Daleks were reused for “The Invaders”. Two of these were borrowed back from Barnardo's children's home in Ilford, London, to which they had been donated following the broadcast of the original serial. Two new Daleks were also constructed by Shawcraft Models. For the first time, Nation's scripts indicated different levels of authority amongst the Daleks, with the introduction of a Dalek Supreme; it would be represented by one of the original casings, repainted to give it a distinctive colour scheme.

It was now known that “The Invaders” would enjoy an extensive amount of location filming, well in excess of what Doctor Who had previously enjoyed. To date, only The Reign Of Terror had benefitted from exterior shooting, and then only for three brief scenes, recorded on a single day and involving none of the regular cast. “The Invaders”, on the other hand, was allocated four days on location, and all of the principal actors would appear along with several supporting artistes. With this in mind, designer Spencer Chapman gave the Daleks large fenders to aid movement. He also added a radio dish to the casings, to explain why the Daleks were no longer confined to the metal floors of their city on Skaro, as in The Daleks.

Assigned to direct “The Invaders” was Richard Martin, who had also been responsible for three episodes of The Daleks. Martin had most recently directed the first episode of Inside The Spaceship in January. He was originally earmarked for the preceding serial, Planet Of Giants, before being switched to “The Invaders”. To play Jenny, Martin cast Ann Davies. The actress agreed to dye her dark hair blonde so that she would be more easily distinguished from Carole Ann Ford, but would not do so until after the location dates. Consequently, Davies would hide her hair under a balaclava during pre-filmed material.

The first location day for “The Invaders” was August 23rd, for material in which Barbara, Jenny and Dortmun travelled across London, and which established the Daleks' dominance over the city by capturing their presence at several major landmarks. Martin and his team visited several locations in or adjacent to Westminster -- Trafalgar Square, the Houses of Parliament, Westminster Bridge, the Albert Embankment -- as well as the Royal Albert Hall and the Albert Memorial in South Kensington. At Trafalgar Square, Spencer Chapman raised the ire of the police when he used blanco to put Dalek markings on some of the monuments. Cast and crew then travelled to Wembley, where the Palace of Industry posed as the museum in which the rebels were headquartered. Road scenes were also filmed at nearby Third Way.

Almost all of the remaining location material was also shot in London. On August 25th, Barbara was conveyed to the rebel hideout via the disused Wood Lane Underground Station in Shepherd's Bush, while the warehouse investigated by the Doctor and Ian was at St Katharine Docks in Wapping. On the 27th, sequences at the river were recorded at the Kew Railway Bridge, Hammersmith Bridge, Irongate Wharf at Wapping, and -- perhaps most famously -- Queen's Wharf in Hammersmith, where a Dalek emerged from the waters of the Thames for the cliffhanger to episode one. More warehouse scenes were shot at Butler's Wharf in Southwark. The only day spent outside of London was August 28th, when John's Hole at Stone in Kent served as the Dalek mine. This was the first of many instances of a quarry being used as a location for Doctor Who.

Beginning on September 3rd, the newspapers revived the story of Carole Ann Ford's imminent departure. Around this time, her last serial was renamed The Dalek Invasion Of Earth (with “The Daleks In Europe” possibly also considered). Just prior to the taping of episode one, World's End, on September 18th, David Archer's surname changed again, to Campbell. This day also marked the relocation of Doctor Who to a new production home: Riverside Studio 1 in Hammersmith, London. Doctor Who's original facilities, Lime Grove Studio D, had rapidly proved to be too archaic and cramped; in recent months, the show had bounced back and forth between several different venues while awaiting Riverside's availability. As usual, all six episodes were recorded on consecutive Fridays.

On October 2nd, William Hartnell's back was injured during camera rehearsals for episode three

Part two, The Daleks, was completed on September 25th. This was the only day that the Dalek Supreme appeared in black-and-grey livery; it was painted completely black for the rest of the story. On October 2nd, during camera rehearsals for the third installment, Day Of Reckoning, William Hartnell's back was injured during the scene where the Doctor was carried on a stretcher down the Dalek saucer ramp. The actors playing the Robomen and the captive humans had been instructed to break step while traversing the ramp, but had failed to do so. This weakened the integrity of the structure, causing it to collapse. Fortunately, Hartnell was well enough to continue with the day's shooting.

As the following week progressed, however, Hartnell was still experiencing pain. After correspondence from his lawyer, the BBC agreed to pay for diagnostic imaging, which indicated no permanent trauma to the spine. Nonetheless, it was agreed that Hartnell would be released, with pay, from the recording of The End Of Tomorrow on October 9th. The Doctor appeared in only one scene to begin with, making it straightforward to modify the script. Originally, it was he who noticed the Dalek firebomb; now, David would make the discovery. The Doctor instead collapsed at the very start of the scene, and the dialogue written for him was shared between David and Susan. Edmund Warwick, who had played Darrius in The Keys Of Marinus, was hired to stand in for the absent Hartnell.

Happily, Hartnell was able to return for the start of rehearsals on part five, The Waking Ally. The day before its October 16th recording, Britons went to the polls for a General Election (in which Harold Wilson became Prime Minister by virtue of a narrow Labour victory). As a result, no videotape machines were available, necessitating Martin's decision to record on 35mm film instead. The previous Friday, Shawcraft's Slyther costume had made a rather ineffectual debut; during the intervening week, the company made a number of enhancements.

Doctor Who's first production block -- and Carole Ann Ford's tenure on the programme -- culminated in the recording of Flashpoint on October 23rd. This was a fraught experience, with the technical complexity of the episode exacerbated by a number of equipment failures. William Hartnell was particularly frustrated, and wound up forgetting portions of the Doctor's farewell speech to Susan.

The Dalek Invasion Of Earth also marked the end of David Whitaker's time as Doctor Who's story editor, due to commitments he had previously made to other projects. However, he had already agreed to write the next serial in production, The Rescue, which would introduce new companion Vicki. Whitaker would also help write the screenplay for the feature film version of The Dalek Invasion Of Earth, produced by Milton Subotsky in association with Aaru Pictures. As with Dr Who And The Daleks (the big-screen version of The Daleks, to which Whitaker also contributed), Daleks: Invasion Earth 2150 AD starred Peter Cushing as human scientist “Dr Who” and was directed by Gordon Flemyng. It premiered on July 22nd, 1966.

Verity Lambert now had enough experience as producer to carry on without an associate producer

Whitaker's replacement as story editor was Dennis Spooner, who had started trailing Whitaker on August 6th; Spooner had recently written The Reign Of Terror. The change-over formally occurred on October 31st, by which time Whitaker had already completed much of the groundwork for the early portion of the second recording block. Also winding down his involvement in Doctor Who around this time was Mervyn Pinfield, who had been serving as the programme's associate producer. It was now felt that Lambert had enough experience as producer to carry on without additional supervision; the post of associate producer was therefore abandoned.

The broadcast of World's End coincided with a reconfiguration of the BBC's Saturday evening schedule. Doctor Who now aired at 5.40pm, twenty-five minutes later than when Planet Of Giants was transmitted. It effectively swapped places with Juke Box Jury, which now preceded Doctor Who. This meant that The Dalek Invasion Of Earth led into a news update, followed by the eleventh season of the police procedural Dixon Of Dock Green. On December 26th, the broadcast of Flashpoint was delayed until 5.55pm, to accommodate the inclusion of the 1946 family film Black Beauty in the Boxing Day schedule.

Although the Daleks had been very popular after their initial outing, the scheduling of The Dalek Invasion Of Earth during November and December inspired a surge of Dalek-related hype throughout the holiday season. Christmas 1964 saw dozens of items of Dalek merchandise invade store shelves. Riding this wave, The Dalek Invasion Of Earth became the series' most successful serial to date, hitting highs of 12.4 million viewers, and making Doctor Who one of the week's Top Ten television programmes for the first time.

• Doctor Who Magazine #280, 28th July 1999, “Archive: The Dalek Invasion Of Earth” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #7, 12th May 2004, “I'm Into Something Good” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #4, 2017, “Story 10: The Dalek Invasion Of Earth”, edited by Mark Wright, Hachette Partworks Ltd.
• Doctor Who: The Handbook: The First Doctor by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing.
• Doctor Who: The Sixties by David J Howe, Mark Stammers and Stephen James Walker (1992), Virgin Publishing.