In 1972, Malcolm Hulke and Terrance Dicks co-authored a book called The Making of Doctor Who.
Doctor Who was just barely old enough to have a history (a whole nine years) and the book mythologised that history. It told us about the creation of Doctor Who; described the filming of a typical story; provided a pseudo-scientific explanation of the TARDIS’s dimensions and even included a religious essay by a vicar.
The core of the book was a summary of the Doctor’s adventures, in the form of in-universe texts. There were Time Lord's legal documents relating to the Doctor's trial and exile; and memos from the Brigadier to Geneva about his new scientific adviser. The actual stories aren’t referred to by name; although there is a chart listing them by production code. Geeky Doctor Who fans could have endless fun cross-referencing the summaries in Making of Doctor Who with the synopses in the Radio Time Tenth Anniversary Special. Because that was all there was.
The Time Lord legal documents refer to the Accused as "∂³ Σ x²". The editorial material says that this is the Doctor's “real name”: a mathematical formula.
Dicks and Hulke were closely involved in the creation of Doctor Who lore-- they were the ones who came up with the idea of Time Lords, probably the most important pillar of the mythos after the TARDIS itself. This doesn't make their every breath canonical. But it is striking that the book gives the Brigadier’s first name as “Alistair”, something not mentioned on screen until Planet of the Spiders.
In 1980, Marvel Comics reprinted the comic strips from Doctor Who Weekly in an American format. Editor Mary-Jo Duffy wrote a text feature bringing readers up to speed on who the Doctor was. Her essay states, parenthetically, that the Doctor's “real name” is ∂³Σx², as if that was a generally established fact. This strongly suggests that the Making of Doctor Who was in use as a “series bible”—or just possibly, that there was a separate internal document that the book drew on.
The point of calling the Doctor “∂³Σx²” is that his name is unpronounceable to humans. If one read the formula off the page it would be something like “derivative cubed sigma ex squared"; but presumably the signs have a Galifreyan meaning distinct from human algebra. In the Three Doctors (also written by Bob Baker and Dave Martin) one of the Founding Fathers of the Time Lords is referred to by the single Greek letter Omega. In other stories, Time Lords have titles like the Doctor (the Master, the Monk, the Valeyard) or what appear to be straightforward forenames (Borusa, Morbius, Romanadvoratrelundar.)
Now, in Armageddon Factor, the Doctor encounters Drax, a Time Lord (or at any rate Gallifreyan) technician who he knew as a student. We aren’t specifically told that they attended the Time Lord Academy: simply that they were on a “tech course” together. [1] Very interestingly, Drax refers to the Doctor by name. And the name he gives him consists of two Greek letters: Theta Sigma. The Doctor asks him to call him Doctor, but he persists in saying “Theet".
If Bob Baker and Dave Martin, like Mary-Jo Duffy, were working from the Making of Doctor Who they might have assumed that the ∂ was a Greek letter and wrongly guessed that it was a “theta”. Or they might have made up the Theta part. (There's a cursive form of theta which looks a lot like the partial derivative sign: so someone who had studied Greek but didn't use it much might mistake one for the other.)[2] There is no particular reason why "Θ Σ" couldn't be an ironic contraction of "∂³Σx²": in the same way that Peggy is short for Margaret and Jack is short for John. In the Happiness Patrol, the Seventh Doctor states unequivocally that Theta Sigma was a college nick-name.
This seems to be an example of canon-drift. A fact, detached from its original narrative context has become something which “everybody knows”. The whole point of Hulke and Dicks coinage of “derivative cubed sigma ex squared” was that it was a miraculous name; a name which underlined the pure alienness of the Time Lords. If the letters simply translated into sounds, then the Doctor might as well have been called “Deesexxx”. The idea of a Time Lord who presents as a South London Car Mechanic; and who trivially calls the Doctor “Theet” removes the very sense of otherness that the name was supposed to suggest.
A contemporary letter-writer to the DWAS fanzine TARDIS said that revealing that the Doctor is called “Theeta Sigma” had exploded the last vestige of mystery from the character. Which is partly true: although the taboo of speaking the Doctor's name has largely been imagined by fans; and is rarely a plot point in the actual story. [3]
Objectively, it is hard to see how knowing that the Doctor is called Theeta Signma spoils Doctor Who. Ribos Operation wasn’t ruined because we know that beyond the control room, the TARDIS is made of bricks and mortar. Face of Evil is not spoiled because the Time Lords turned out not to be quite as mysterious and omnipotent as we once thought. Destiny of the Daleks and Creature from the Pit would be the same stories if the Doctor's name had remained an ultimate mystery.
But this stuff does tell us something about the tone of the series and the style that Read and Williams and Adams are bringing to the show. To say “irreverence” implies that Doctor Who has a quality of holiness which deserves respect, which is obviously absurd. (This was very slightly before Life of Brian.) But it is quite true that the show has become more and more playful. Nothing is off limits; the present scene and the current one-liner are all that count, continuity and world-building be damned. The idea that the Doctor had a silly nick name at college--and that he is annoyed and embarrassed when an old mate uses it--is fun in the moment. But if you see it as making an irrevocable addition to the backstory, it's at best pointless and at worst destructive.
The Doctor is not David Copperfield. He’s not even Conan the Barbarian. The Hyperborean Legion invented facts about Conan the Barbarian that surprised Robert E Howard: but pretending that Conan was an historical character about whom facts could be invented was very much in tune with the game Bob was playing. Doctor Who--the Doctor Who of seasons fifteen, sixteen and seventeen--is a quite different beast.
The incumbent producer and the incoming script editor have laid their cards on the table. This is not your grandfather's Doctor Who.
Fans rejected the approach: Season 17 was universally despised. In 1983 an essay in the programme for the infamous Longleat twentieth anniversary celebration (author: Levine, I) stated, unequivocally, that Graham Williams’ approach was bad-wrong and that John Nathan-Turner fixed everything in the early 80s.
What will Doctor Who be like from now on? The Key to Time asks the question. Season 17 answers it. Minotaur in y-fronts; Time Lords fellating alien tentacles; cameos by comedians and heroes who howl “my arms! my legs! my everything" when they are injured.
Is this the moment when Doctor Who truly became itself? Or the day the series died?
[1] This was 450 years ago. The birthday scene in Stones of Blood would have established the Doctor’s age as 751; making the Doctor 300 years old when he was a student; which is fairly consistent with the Doctor’s apparent age of around 45. In Power of Kroll he gives his age as “nearly 760”.
[2] Thanks to Patreons KD & DG for this scholarly observation!
[3] Ian Chesterton asks “doctor who?” in the second episode; a soldier asks the same question in the Highlanders; and famously the Post Office Tower computer thinks Doctor Who is his actual name; but I don’t think the words are spoken again until Tegan blurts “doctor whoever you are” in Baker’s final story.
Available to Patreons -- The Androids of Tara
Available to Patreons -- The Power of Kroll
Available to Patreons -- The Armageddon Factor
Or read my compleat Key To Time essays in PDF booklet.