Ah, Classic Doctor Who. 42 years, 26 seasons, 8 leading men, 30 main cast, 695 episodes, 155 serials and one TV movie—plus two mid-60s theatrical releases. Such a depth of history can be daunting for the newer Who fan, brought into this Gallifreyan exile’s adventures via Doctors Nine through Eleven, since the excellent 2005 reboot.
Add in some natural reluctance resulting from the show’s early reputation for shoddy production values (and yes, the sets really do shake sometimes), an unfamiliar story-telling format (it’s just constant “To Be Continued” plot arcs, one after the other), as well as the inevitable confusion resulting from the legendary “Missing Episodes” (master tapes ruthlessly recycled by a thrifty BBC, back when they knew not what they did), and it’s really no wonder that many consider New Who to have granted them back story enough, and that the decades-spanning stories preceding it—many in black-and-white!—are just not worth the effort.
But there is much delight and wonder to be found in the early escapades of this ancient, time- and space-travelling whimsical genius; it would be a shame for them to remain entirely unexplored by even the most recent of Matt Smith-era converts. To make it all a little easier to digest, then, I’ve assembled a “Best of” selection for each of the Doctor’s earlier incarnations, listing the unmissable serials that will surely help explain many puzzles of the Whoniverse, as well as entertain and amuse—although, admittedly, not always for the right reasons. (The outfits alone!)
We start, of course, with:
THE FIRST DOCTOR
Played by: William Hartnell
First Appearance: “An Unearthly Child” (An Unearthly Child, 23 November, 1963)
Last Appearance: “Episode 4” (The Tenth Planet, 29 October, 1966) *MISSING*
Episodes: 134
Serials: 29
Seasons: ~3.2
Style: Dickensian chic.
Characteristics: The First Doctor is a fussy, elderly grouch with luxuriant silver locks, a deceptively frail form, and an often patronizing demeanor. However, as the first incarnation of the Doctor’s potential (at this stage) thirteen personalities, it eventually transpires that though he has inhabited this particular body for about 450 years, he is still considered something of an adolescent by the standards of his long-lived people.
Companions: In addition to travelling with his granddaughter Susan (Carole Anne Ford), in an effort to educate her about the universe, the First Doctor abducts her teachers Barbara (Jacqueline Hill) and Ian (William Russell); gives refuge to orphan teen Vicki (Maureen O’Brien); unknowingly rescues space pilot Steven (Peter Purves); liberates Trojan slave Katarina (Adrienne Hill); is plagued by the tiresome Dodo (Jackie Lane); and welcomes sophisticate Polly (Anneke Wills) and sailor Ben (Michael Craze).
THE ESSENTIALS:
1. AN UNEARTHLY CHILD, Season 1, Episodes 1-4
Written by: Anthony Coburn
Directed by: Waris Hussein
Setting: 1963 Earth; 100,000 BC Earth
4 Episodes: “An Unearthly Child” (November 23, 1963), “The Cave of Skulls” (November 30, 1963), “The Forest of Fear” (December 7, 1963), “The Firemaker” (December 14, 1963)
It may seem a little obvious, the idea that one would start with—gasp!—the pilot episode of a series in order to come to grips with its venerable beginnings, but the fact is, the first half-hour installment of this serial, also called “An Unearthly Child,” cleverly sets up the next fifty years of intriguing mystery, chaotic adventure and high-handed interference in other cultures. To wit: the enigmatic Doctor and his erratic granddaughter Susan bedevil that young lady’s two very curious teachers with an old Police Box (bigger on the inside than on the outside), and then inadvertently whisk them off to become pawns in a Paleolithic power struggle. Oh, the serial is chock full of troubling “isms”—sexism, imperialism, flat-out racism, it’s all here—and one can’t help but feel that letting the scatterbrained Susan “Of course, the decimal system hasn’t started yet!” Foreman out of his sight on 1963 Earth calls the Doctor’s wisdom somewhat into question. On the other hand, this is a theme that is often revisited throughout the series, and so it’s nice to see its genesis: the Doctor may be brilliant, but he really doesn’t have much commonsense.
EXPLAINED! Why the TARDIS still appears “camouflaged” as a Police Box, even when such things don’t exist anymore.
2. THE DALEK INVASION OF EARTH, Season 2, Episodes 4-9
Written by: Terry Nation
Directed by: Richard Martin
Setting: Late-22nd Century Earth
6 Episodes: “World’s End” (November 21, 1964), “The Daleks” (November 28, 1964), “Day of Reckoning” (December 5, 1964), “The End of Tomorrow” (December 12, 1964), “The Waking Ally” (December 19, 1964), “Flashpoint” (December 26, 1964)
There are some who might contend that the first appearance of this most iconic of the Doctor’s foes (in the aptly titled earlier serial, The Daleks), might be better placed here, but frankly it is in this, their second appearance, that they truly come into their own as viable, series-long, hide-behind-the-sofa-in-terror-of villains. The Dalek Invasion of Earth sees actual location shooting employed for the first time in Who history, with the giant metallic shuttlecocks trundling around a modern/future London, not actually promising to “Exterminate!” folks left and right just yet, but y’know. It’s implied. This serial is also notable for the departure of Susan (I know; you just met her!), when she falls in love with a resistance leader and is left behind by a selfless grandfather who surely was at least a little grateful to be spared her shrill histrionics throughout his further travels.
Another possibility here is to watch Daleks—Invasion Earth 2150 AD, the 1966 slightly reimagined theatrical version starring Peter Cushing, but while you will certainly still get the gist of the action (and, hey! It’s in color), it is the original Doctor, Susan, Ian and—above all!—Susan’s elegant history teacher Barbara, who make this story the enduring awesome it is.
EXPLAINED! The Doctor’s ongoing need for young female—platonic!—companionship.
3. THE TIME MEDDLER, Season 2, Episodes 36-39
Written by: Dennis Spooner
Directed by: Douglas Camfield
Setting: England, 1066
Episodes: “The Watcher” (July 3, 1965), “The Meddling Monk” (July 10, 1965), “A Battle of Wits” (July 17, 1965), “Checkmate” (July 24, 1965)
Arriving on the English coast in the 11th-C, the Doctor, Vicki and Steven discover that they are not the only time travelers in the vicinity. A mischievous member of the Doctor’s own—still unnamed—race has taken up residence in a nearby monastery, his aim to aid King Harold to defeat the oncoming Norman army, thereby robbing their leader, William, of his “the Conqueror,” and usher in an era of peace and enlightened prosperity. Steven, meanwhile, very new to this whole time travel caper, is adorably flummoxed by events all the way through—really, his is one of the most realistic reactions to such an extraordinary set of circumstances evinced by any of the Doctor’s young associates, and he and Vicki also have some lovely sparky banter.
And there are so many firsts in this episode! It’s an historical tale but also includes sci-fi; it’s the first time we encounter another from the Doctor’s homeworld; the use of anachronism is actually deliberate here; and we learn what TARDIS stands for (extraneous “s” notwithstanding). Also, this one has Vikings!
EXPLAINED! The rules of time travel in the Whoniverse… kind of. Also, how Stonehenge was built! (You knew it had to be aliens, right?)
4. THE ARK, Season 3, Episodes 26-29
Written by: Paul Erickson & Lesley Scott
Directed by: Michael Imison
Setting: Space!
Episodes: “The Steel Sky” (March 5, 1966), “The Plague” (March 12, 1966), “The Return” (March 19, 1966), “The Bomb” (March 26, 1966)
Now this one is going to be controversial, as it is assuredly not a common favorite, but The Ark just contains so many clever concepts that it is an absolute gem of science fiction-as-parable-ness, and cannot go overlooked. There’s post-apocalyptic dystopia! Accidental plague! Courtroom drama! Slavery allegory! Genetic engineering! Plus the Doctor lives up to his title and cures the common cold. (Though… keeping people with fevers warm, Doctor? Medicine is… different, where you come from.)
More than anything, though, this serial is notable for its narrative style, the way in which it wraps up one crisis in two of its four installments, and then checks back in 700 years later to discover just what the Doctor’s interference has wrought in the interim. Many Doctor Who episodes have dealt with consequences, but none have so dramatically brought home just how damaging, and how dangerous, this capricious time- and space-travelling can be. It would be one thing if Doctor Who followed an “it happened therefore it has always happened” style of time travel, but instead it allows time to be mutable, which means that his presence here in the year 10,000,000 AD (yes, that is 10 million), where the last vestiges of humanity are on a generation ship on their way to a new planetary home, impact greatly on the survival of the entire human race.
The biggest downside of this one is that it is a Dodo story, and Dodo is by far the Doctor’s most irritating companion ever, but Steven’s pompous hilariousness more than makes up for her. And, oh, those future spaceship uniforms! Sexy.
EXPLAINED! Why the Doctor doesn’t tend to travel too far into humanity’s future any more.
5. THE TENTH PLANET, Season 4, Episodes 4-7
Written by: Kit Pedler and Gerry Davis
Directed by: Derek Martinus
Setting: 1986 Earth, the South Pole
Episodes: “Episode 1” (October 8, 1966), “Episode 2” (October 15, 1966), “Episode 3” (October 22, 1966), “Episode 4” (October 29, 1966)
As touched on earlier, one of the tragedies of Doctor Who is the fact that there are so many episodes that remain completely absent from the record. Every now and then one will still crop up—a censored version of an early tale will be found at a regional station in Nigeria, for example (this actually happened)—but the reality of Classic Who is that 106 of the first six seasons’ 253 episodes are just gone. Sadly, one of these is the final chapter of The Tenth Planet, which means that while we get to enjoy three-quarters of the first story featuring the menacing, Borg-inspiring Cybermen as they attempt to drain Earth of its power and, er, assimilate its population, the thrilling finale only comes to us as a soundtrack, some on-set stills, and—oh, pivotal moment!—actual moving images (in both senses), as the Doctor undergoes his first regeneration.
This is not to say that the tireless Doctor Who Restoration Team has not done a bang-up job of it, all things considered; it’s just that the flick book-like recreation of “Episode 4” remains an ongoing source of sorrow that such a thing is even necessary. Nevertheless, The Tenth Planet is a must-see, for the blank-faced, early GPS-voiced Cybermen (who can speak before their mouths even open!) as much as for the unprecedented metamorphosis of its star. Plus, in 1986, the International Space Command is building a base on the moon! Yeah, remember when that happened?
EXPLAINED! The origin of the Cybermen; the apparent limits a Time Lord’s body.
Of course, this is all just the recommendation of one humble Whovian—there are doubtless others who can make convincing arguments for The Aztecs or The Space Museum or, hell, The Web Planet as the greatest of all First Doctor adventures. (Well, okay. Probably not The Web Planet.)
Have at it!
NEXT TIME: The Second Doctor—The Manic Prankster
Rachel Hyland is Editor in Chief of Geek Speak Magazine.
Surprised to see The Ark get love.
I misremembered the episode for years–I thought the two “halves” of the episode were really two seperate stories, rather than being part of the same serial. I had misremembered-thought it was cool two seperate stories took place on the Ark 700 years apart.
Possible correction: The meaning of TARDIS came in An Unearthly Child when Our Motley Crew first come on board and Susan says “Tardis—Time And Relative Dimensions in Space—that’s what I call it”
Although later canon says this is a generic term for all Timelord ships; why Susan claimed to have invented this term is unclear. Unless she is an early regeneration of Rassilon and actually DID coin the term…
Which fits with my nightmare scenario of Thanksgiving at the Who’s (Whose?):
Dr. and River Who sit down with the family: The and Jenny Master, the in-laws (Amy and Rory), and little Susan who gets to carves the roast…
Not as complicated as the Once Upon A Time holiday dinner but it’s bad enough!
Just a suggestion to the mods, but for the blog posts (such as this, and the various rewatches) that are regarding TV episodes, it would be awesome to include a list of links where the shows can be downloaded/streamed/purchased on DVD as a convenience for those following along :)
We’re trying to keep this list to just four stories? It’s awfully tough to leave out “The Aztecs,” given that it’s a traditional historical, which the early years were known for, and it displays considerable awesomeness on the part of both Barbara and Ian. I think you could get away with “The Space Museum” as a good substitute for “The Time Meddler” if you want to highlight the timey-wimey-ness being present from the get-go. I could also make a good argument for “The War Machines” as an early example of the Doctor’s modern-day adventures, which were obviously a Pertwee thing, but also very present in the modern series. Plus, Dodo’s barely in it.
While I’m not a big fan of Dodo, “by far the Doctor’s most irritating companion ever”? Did you block all memory of Peri from your mind? I – I – I don’t think she ever says a single sentence without stuttering in fear. And that’s leaving aside her “accent.” She definitely got a raw deal in that she lost the Doctor she signed on with almost immediately, but I could never figure out why Six didn’t just abandon her on the nearest planet, habitable or not.
So, I’m not really familiar with Classic Who and all the efforts to recapture the missing episodes.
But have they ever tried to re-film some of them? At lease the death of the first Doctor Who. I know, different everything, so it won’t be the same. But it would be easier to see for the modern audience than a “flip book”, as you said.
Braid_Tug, a very few of the missing stories have had their gaps filled in with animation, so that the stories can be released complete. So far, that’s been the Second Doctor story “The Invasion,” the First Doctor story “The Reign of Terror,” and coming out soon is “The Tenth Planet,” mentioned above, which ends in the Doctor’s first regeneration. The animation is Flash-style, so it can be kind of static, and perhaps not to everybody’s taste. It certainly does tend to jar with the live-action episodes around it, but the animators have been careful to match the sets and costumes as closely as possible. It’s not perfect, but I don’t think there is a perfect solution.
@@@@@ Prince Jvstin
I know, it’s definitely not a universal fave, but I really think it gives a huge insight into the series as a whole, and especially highlights the difficulty with all the time-travel-on-a-whim. And I can see why it’d be easy to confuse the one story with two! I’ve actually often wondered if it was perhaps originally intended to be two separate serials, but then there just wasn’t enough material for it.
@@@@@ Dr. Thanatos
Yep, it’s that “at least that’s what I call it” that clinches The Time Meddler as our first real knowledge of what TARDIS means. Until then, it was just Susan’s cute made-up definition…
Meanwhile, I would so very adore it if someone in New Who explained the meaning with: “Time and Relative Dimension in Space, or NAMBLA.”
@@@@@ Brian Mac
Five stories, actually, but yes, that is my brief. The Second Doctor (covered next week) is the last of the relatively easy ones… then the Missing Episodes cease to narrow my choices, and it all gets a bit tricky. But fun!
Speaking of the Missing Episodes, The Ice Warriors has also recently been released with animated recreations of its two missing eps, and it’s very well done indeed.
@@@@@ Braid_Tug
Probably the best thing about the animated recreations (and even the valiant “flip book” efforts of the Restoration Team) is that they use the original audio, taped by nascent young Whovians straight off the telly in the show’s original run. So at least we get to hear the Doctor and his companions and their friends/foes as was originally intended, warts and over-acting and all. I like that.
They used different animation styles for “The Invasion” and “The Reign of Terror”. I find that the new animation style (“The Reign of Terror”) is quite jarring from the live action because it is mostly done in close-ups. It appears to be one talking head after another. They will occasionally show sets but the quick cuts between close-ups when characters are talking to one another is really distracting. The previously animated episodes (“The Invasion”) made some mistakes but at least it kept closer to the the period’s style of shooting episodes.
This is just nit-picking though because it’s better than nothing. I’ve managed to listen to all of the missing episodes and some of them are a chore to get through (I’m looking at you “The Massacre of St. Bartholomew’s Eve”.)
Oh, awesome. :) I live in a household with long history with the Doctor, but didn’t really come into the fold of the fandom until the newer incarnation of the series. But then I told my Classic-era loving housemate that I wanted to get an idea of some good classic episodes, especially about the Daleks. So he said to me, “You want Daleks? I gotcher Daleks!” He went downstairs, grabbed all his DVDs of Dalek-themed episodes, and brought ’em upstairs to me to plunk ’em down in front of me.
That turned out to be a surprisingly good way to get an overview of most of the classic-era Doctors!
@@@@@ Brian Mac
Oh, and re: companions and their relative levels of irritatingness. I would put Peri on a par with Victoria and Mel: completely useless, and sure, annoying, but more to be pitied than despised. I dislike NO ONE in this series with the same intensity that I do Dodo — and yes, I am including Adric in this.
I would definitely count “The Aztecs” as essential. It’s a ripping good yarn, it’s historically well-researched (though with its share of White Man’s Burden condescension), it’s probably Barbara’s best story, and it’s the first Doctor Who story — and one of the few in the entire original series — to deal with the possibilities and ethics of changing history (although its take on the issue differs from that of later stories). So even though “The Time Meddler” is the first historical serial to introduce SF elements other than the TARDIS crew, I would say that “The Aztecs” is very much a science fiction story, because it explores the ramifications of time travel in a way Classic DW rarely did.
“Marco Polo” and “The Crusade” would also count as essentials if they survived. They’re just really good. “The Crusade” has a wonderfully BBC-Shakespearean quality to it, as if we’re seeing a production of a lost History of King Richard I which the Doctor Who cast has stumbled into.
As for the most irritating companion, I hate to say it, but I’d pick Victoria. She started out promisingly in “Tomb of the Cybermen,” but in the surviving episodes I’ve seen from later in her season, she just got more and more helpless and terrified and screaming all the time.
Peri was pretty annoying in her first season or so, but she’d mellowed by “Trial of a Time Lord.”
@2: It’s doubtful that Gallifreyans would use an acronym based on 20th-century English. And we know that the Doctor’s TARDIS translates all languages for those who travel in it (and for the viewing audience as well). So my take is that when we see Time Lords referring to their craft as TARDISes, that’s actually a translation from whatever the actual Gallifreyan term is. They’re not really saying that word any more than they’re speaking English.
First, if you’re going to watch classic Who, especially Hartnell, if you haven’t looked at the Wife In Space, you’re missing out. A dedicated fan makes his non-fan wife watch every single episode and recon of the classic era, and they’re conversation provides running commentary. Frequently funny, and insightful.
Second, I made a similar list for some friends a while back – a list of episodes to watch to introduce people to each Doctor. My rules – no recons, shorter is better, and provide beginner, intermediate, and advanced stories for each Doctor, so watchers could dial in their level of geekery and comittment.
For Hartnell, my beginner episode is “An Unearthly Child.” Not the whole seial, mind you, which is crap, but just the episode. It’s attachment to the rest of the serial is pretty minimal, the episode is delightfully atmospheric, and gives you a real glimpse of what’s the same and what’s different about the early Doctor.
Intermediate story is “The Time Meddler”. It’s the one that feels most like modern Who. It’s got a warm, approachable Doctor, a mix of history and science fiction, a genuine mystery, and it’s really funny. Hartnell is on fire in his performance, clearly having a ball, which is a big deal watching some of those First Doctor stories – you never knew if Hartnell was going to be up to it or not.
Advanced: The Daleks! I get torn between that and The Dalek Invasion of Earth, but I figure the first story is the best one, though I could be persuaded the other way for obvious reasons.
Bonus! The Romans – Dennis Spooner is one the writers I’d like to see brought back from the grave to write again for the new series. Nice to get a proper historical in, and once again, the cast is nailing it and the script is charming and funny. An easy pick.
I would second The Romans. It’s one of the funniest moments in the 60’s Doctor Who. And the 2 part “The Rescue” right before it, which has an absolutely brilliant twist.
edit: no way you’re gonna be able to cut Tom Baker down to 5 stories.
@@@@@ 9. Kudzu
You’re right about the differences in style — different animation companies are given the task in each case — and THANK YOU for putting your finger on what it was that was bothering me so much about the addition to The Reign of Terror!
As to St. Batholemew’s. Yes, so tedious. It’s like if you could only listen to the Senate scenes of Episode I, without at least the slight mitigating coolness of the CGI and costuming.
@@@@@ 10. annathepiper
Sometimes it feels like all they did was put assorted nouns in front of the words “and the Daleks”, they got so popular — Power of the Daleks, The Planet of the Daleks, Destiny of the Daleks, etc. — and they are pretty ubiqitous throughout, which means their adventures are certainly a good series primer. Except that then you completely ignore the Cybermen, the Autons, the Silurians… though I guess you do get a glimpse of the Master in Frontier in Space. Another way to go would be to watch all of the (existing) regeneration episodes/serials, I suppose…
@@@@@ 12. ChristopherLBennet
An excellent point about The Aztecs — I guess I feel my beloved The Ark covers something of the same philosopical ground while also not making of the Doctor SUCH an outright hypocrite (warning Barbara about changing history? The nerve!), and with An Unearthly Child also filling the “historical” spot, I had to make a tough choice. In fact, if I was going to include another historical here, it probably would have been The Romans. (I WISH I had seen The Crusade!)
And yes: Victoria. Pah! She comes in for her fair share of disdain in the Second Doctor rundown, don’t you worry.
Also, re: TARDIS definition: you know, I had never even considered it from that point of view. But since the TARDIS not only translates the language people are speaking but also manages to make their lips move as though they are speaking it (and then gives some of them exotic accents for no particular reason), I’m just going to add it to the pile of mysterious linguistic-related craziness with which this show is populated, and accept that it will never really make sense.
@@@@@ 13. ErikHarrison
Wife in Space! I hadn’t encountered that before. So much fun — good call.
@@@@@ 14. jerec84
I always find The Rescue spends way too much of its short running time mourning the recent departure of Susan, whom I am all too happy to have seen the back of. And cutting the Fourth Doctor down to five “essential” stories… well, I have managed it, but it’s probably not going to make anyone terribly happy.
I still laugh at the ultra closeup of Susan near the beginning of “An Unearthly Child” where she says, “Space.”
Of course Susan calls it the TARDIS. She’s unlikely to use her grandfather’s name for the vessel. What grand-daughter do you know of that would even admit to a grandparent that used the word ‘Sexy’ let alone used it as the name for their vessel?
Glad to see someone made the correction of when we learned what TARDIS meant.
I know it’s very hard to pick the most essential stories but skipping The Aztecs was a mistake. It is not only a gorgeously produced serial, but it is the first Doctor Who epsiode to really tackle historical facts accurately in the series, Jacqueline Hill’s performance as Barbara is an absolute season highlight and we see the Doctor’s sensitive and dare we say love-struck side.
I have a great personal fondness for Edge of Destruction as that’s where we first explore the potentially destructive implications of time travel but it’s not necessarily a “vital” episode.
I am going to have to quibble with including “The Ark,” as this represents one of the more shamefully racist moments in Doctor Who history. Hmmm, a story about dark-skinned servants who rise up and become cruel masters the moment they get a chance? And who manage to bungle the whole slave-master business by being completely stupid in the bargain? That’s just icky. Plus, the entire sequence set on Refusis is incredibly dumb and hacky, with the plot piddling out into sheer nonsense around about the middle of episode 3.
The “science” in this story is some of the least plausible the series ever managed (which is saying something, I know), and one gets the sense that nobody behind the scenes cares a single bit about producing anything approaching intelligent entertainment. Sure there are some cool sets, fun moments (“Take them away and lock them in the security kitchen!”) and moments of pleasure scattered throughout, but give it a miss unless you are blazingly stoned/drunk and have a high tolerance for the campiest excesses of the early 1960s.
I know it’s hard to pick great Hartnells with so many missing, but including this as “essential” and giving a miss to “The Aztecs” or “The Dead Planet” is just bizarre. If your attention span only run to four episodes, check out “The War Machines” instead. It’s not without its problems, but it’s got the Doctor in swinging 60s London, a plot that anticipates the internet by quite a few years, and looks, in retrospect, like a trial run for the UNIT years.
How Susan leaves the Tardis drives me crazy. She is a sheltered teenage girl who meets and falls for a guy on a war torn planet and wants to stay. Everyone says great you go play house with a boy you just met in a war zone and is never seen again until the 25th anniversy special? What the hell kind of parenting is that?
@20: Well, technically it’s grandparenting. Also, she may have looked like a teenager, but do we know how old she actually was?
And of course, while the Doctor did memorably promise “I shall be back,” the fact was that he always overestimated his ability to control the TARDIS. He didn’t gain any substantive control over its navigation until his fourth incarnation.
And her return was in the 20th-anniversary special. They didn’t have a 25th-anniversary special, although both “Remembrance of the Daleks” and “Silver Nemesis” commemorated the 25th anniversary.
Idea:
Use David Bradley and the other actors that portrait the First Doctor’s companions in “An Adventure in Space and Time” and produce a short 25 min “lost” episode of the First Doctor and companions adventuring on ‘future’ London (~2014). It could be reasonably cheap to produce and it would be awsome fan service!
Okay, I finished watching: THE DALEK INVASION OF EARTH.
I still don’t know why the Doctor has to travel around with a young girl (+ others sometimes.)
What bit of dialogue did I miss?
But watching the “Goodbye Susan” after seeing him holding her shoe was really moving. You can tell he’s preparing himself. Much more moving than just seeing the clip without the background.
@23: Well, Doctor Who has always been a children’s/family series, so having young people along for audience identification was a good idea. Plus it’s helpful to have human characters, or at least characters of normal intelligence, to serve as audience surrogates, so that the Doctor’s explanations to his companions will explain things to the viewer.
Plus, since the intent was that this was a show for parents to watch along with their children, having a female cast member was a way of throwing in some sex appeal for adult male viewers. Although these days it’s probably at least as much about giving female viewers someone to identify with.