Last on screen appearance of Katy Manning as Jo Grant until her guest appearance in spin-off series "The Sarah Jane Adventures" 37 years later.
According to Richard Franklin, the stage directions called for Mike Yates to look utterly crestfallen when Clifford Jones announces that he and Jo are to be engaged, as Yates was set up to be her romantic interest. That's how he played the scene.
The computer seems to be governed by many of Frederick Nietzsche's political and social policies. He even refers to Stevens as his little "Superman" (Ubermensch), a sociological ideal for man.
The first recognizable tune that the BOSS computer hums is the catchy finale of Beethoven's violin concerto. This is consistently misidentified as the work of Richard Wagner on the DVD release by the subtitler, production text commentator Richard Molesworth, and even writer Robert Sloman in a bonus interview. The computer does have a line about sweeping into power "on the crest of a wave of Wagnerian sound" but never actually hums anything by Wagner.
This episode was watched by 7 million viewers on its original transmission.