Doctor Who was in a perilous state at the end of Patrick Troughton's tenure. Ratings had been in decline - so much so that few of Troughton's stories even survive intact - and there was a strong possibility that if a new series didn't improve matters, there wouldn't be another.
Spearhead from Space is in many ways quite a unique story in the original series history, not only introducing the Third Doctor but also tweaking the format of the show remarkably successfully, with producer Derrick Sherwin using the more Earthbound Quatermass as his model while adding more action to turn it into more of an adventure series. It also has a unique look, and not just because the show made the leap from black and white to colour for the first time. While TV shows were traditionally shot largely on tape for studio interiors and 16mm film for exteriors, a BBC strike meant that Spearhead was shot entirely on film and on location. As well as giving the show a much more cinematic and adventurous look, this also ensured that after proper restoration this probably looks the best of any story from that era, with pin-sharp definition and superb colour on the remastered DVD that is a visible improvement on the previous release.
The Quatermass influence is particularly noticeable in the first half of the story. Like Quatermass II, it begins with meteorites being guided to a specific part of the English countryside where they are collected for a sinister purpose in a secret establishment, although it largely drops the government conspiracy angle that saw Nigel Kneale's invaders taking over the halls of power and using the Official Secrets Act to keep prying human eyes away. There is a half-hearted attempt to gain access to the corridors of power, but here the military is in a more heroic light as the story introduces UNIT and Brigadier Lethbridge-Stewart (previously seen in The Invasion) as series regulars for the now exiled on Earth Doctor. UNIT almost take centre-stage for much of the early running: after a brief appearance in long shot falling out of the TARDIS we don't actually meet Jon Pertwee's new Doctor until halfway through the first episode. Introducing the troubled regeneration theme that the series would consistently return to and which allowed each new Doctor to gradually find his unique character, it set the template for each new Doctor's introduction. Indeed, elements of it would turn up in Paul McGann and Matt Smith's introductions while the Autons would be used as the villains in for Christopher Eccleston's first story in the revamped NuWho. And the Autons prove to be particularly memorable villains, the sequence where shop window dummies come to life and embarking on a killing spree on Ealing high street one of the series seminal images.
Documentary Down to Earth offers a concise and surprisingly frank account of the reinvention of the show, which had only been given a new series because the BBC couldn't come up with a replacement. UNIT's introduction was as much a practical as an aesthetic decision, designed to take some of the narrative strain and limit the amount of lengthy speeches Pertwee had to deal with, since the crippling 44-episode a year schedule and dialogue-heavy scripts had played a big part in an increasingly overworked and cantankerous Patrick Troughton's decision to leave (the length of the run was also drastically reduced to keep the workload manageable). The accompanying featurette on the BBC's conversion from black and white to colour is more technical, especially when detailing the creation of the new title sequence.
The Nestine and their Autons returned the following year in Terror of the Autons, which also saw the introduction of Roger Delgado's the Master, then the diabolical Moriarty to the Doctor's Holmes rather than a tiresome Joker wannabe. The script makes much of their similarities: both trapped on Earth, each thinks the other is almost as brilliant as they are, and each enjoys the other's escapes because it prolongs their duel and sweetens the anticipation of their ultimate victory. The Master wasn't the only new arrival, with Katy Manning making her debut as one of the Doctor's most popular and long-serving assistants. Her job description may boil down to handing the Doctor his test tubes and telling him how brilliant he is, but her enthusiastic personality works wonderfully well in tandem with Pertwee's Doctor and the pair have genuine screen chemistry without ever a hint of the romantic complications of the NuWho seasons.
Offering one of the more surreal images of the series in the form of a Time Lord, dressed as a civil servant complete with bowler and brolly, suspended mid-air outside a radio telescope, it downplays the Autons in favour of the menacing possibilities of a potential enemy to be found all over every home in the country: plastic. The influence is early horror films like Devil Doll and Dr Cyclops (alongside a nod to The Sweet Smell of Disaster episode of Adam Adamant Lives!) as scientists are shrunken and their bodies left in lunch boxes, and plastic chairs, telephones, flowers and grotesque toys come to life and kill people - a particularly pertinent threat in the 70s, the plastic decade that taste forgot. But away from the showstoppers, the Nestines are generally sidelined, little more than pawns of the Master despite hints of some tension and impatience with him.
It's a more complicated plot this time round, though it's consistently marred by the excessive use of especially bad colour separation overlay effects, which here aren't simply used to superimpose actors over elaborate special effect shots but are used to save building basic sets so that even a simple shot of a bit player in a kitchen will look unreal because she's surrounded by thick matte lines as she's overlaid on what's obviously a slide taken from a kitchen showroom catalogue. While you can make allowances for that sort of thing when spaceships, alien landscapes or giant monsters are concerned, it just smacks of laziness and penny pinching when it's used to save money on everyday things.
The highlight of a decent extras package, which also includes documentaries on setting up Pertwee's second season and The Master as well as the usual audio commentary, stills gallery and onscreen trivia track, is a brief featurette on plastic and why it made for such a perfect villain - after all, how can you hide behind your plastic sofa this time round if even that might kill you? Sadly the picture quality isn't a patch on Spearhead. The outside broadcast scenes are particularly poor, looking like bad standards conversions from NTSC, though most of the studio footage is considerably better, and it's still an improvement on the fairly rare video release.