For Peter Davison’s showcase 20th anniversary season, the producers and writers wanted to bring back a number of classic monsters/villains.
However, rather than just go for a straight Dalek or Cyberman return (who would be appearing in the The Five Doctors anyhow). The producers wanted to showcase some less featured monsters/villains.
They decided on resurrecting Omega, the Timelord anti-hero from The Three Doctors and the Black and White Guardians from season 17’s – ‘Key To Time‘ story arc. The Master and more obscurely the Mara from season 19’s surprise standout; Kinda.
Season 20 was split into standalones; The Arc Infinity, Snakedance and The King’s Demons. The finale feature-length special; The Five Doctors and the Black Guardian Trilogy.
The Guardian Trilogy was 3-linked stories, Mawdryn Undead, Terminus and Enlightment; featuring an overriding plot-arc of the return of the White & Black Guardians – powerful god-like beings.
Originally, an episode called Song Of The Space Whale (by Pat Mills) was to be the opener but was abandoned due to cost and the hastily written Mawdryn Undead (by Peter Grimwade) – replaced it.
Also to feature in Mawdryn Undead, was First Doctor companion; Ian Chesterton (William Russell) – who would feature as a teacher but due to other commitments – was replaced by (the now retired UNIT Brigadier) Lethbridge-Stewart (Nicholas Courtney) who had moved into teaching.
Mawdryn Undead featured the interesting premise of an immortal zombie-like alien race; the Mawdryn – who wanted the power of regeneration and were prepared to kill the Doctor; to get it.
Also along for the ride, was an Earth school pupil of the Brigadiers, called Turlough. However, Turlough was really a Trionian alien – under the control of the Black Guardian and with a mission to sabotage the Tardis and kill the Doctor.
Mawdryn Undead featured the clever subplot of Tegan and Nyssa, believing that the Doctor had regenerated but infact; was Mawdryn impersonating him – to gain entry to the Tardis.
Terminus (written by Stephen Gallagher) was largely unconnected, save for the writing out of companion Nyssa from the show and after a promising start, fell into a rather insipid plot of space plague and mercenaries.
The Barbara Clegg penned – Enlightment; got the trilogy back on track. With a spiritual number, featuring the non-corporeal ‘Eternals’; racing old-style Earth sailing ships through space. The Doctor raced onto a final confrontation with the Black Guardian.
The Black Guardian Trilogy was a sequel – of sorts to season 17’s Key To Time, in which the Fourth Doctor was tasked to reassemble the Key To Time – by the White Guardian but chose to scatter it, to keep it out of the Black Guardian’s hands.
The Guardian Trilogy benefitted from a nostalgic reappearance by the Brigadier character, the tortured loyalties of Turlough and a clearing of the companion ranks with the offloading of Nyssa.
The Mawdryn were interestingly conceived and tragic purveyors of their own doom. For once, they were not here to invade Earth – they just wanted to die but kill the Doctor to help that achieve that aim.
Terminus was a non-event that threatened to rob the Guardian Trilogy of it’s built-up pacing. Thankfully, Enlightment picked proceedings up, with a mysterious and atmospheric space-race thriller and eerie turn from the souless Eternals
And whilst all of the spotlight – in the 20th anniversary year, is usually given to the excellent The Five Doctors. Nonetheless, The Black Guardian Trilogy forms an interesting mid-season story-arc and backbone to season 20.
Season Twenty – 1983