This story saw the introduction of a new fibreglass TARDIS prop to replace the battered wooden version in use since 1976.
This introduces many changes including a new theme, title sequence, a new costume for the Doctor, and a new more accurate-looking police box prop.
Production of the serial was extremely challenging. Tom Baker and Lalla Ward's tumultuous off-screen relationship was at a nadir, causing the mood on set to be distinctly chilly. Director Lovett Bickford's management of the shoot caused it to go so badly over budget that John Nathan-Turner was severely reprimanded by his superiors. Bickford would never work on the series again.
The first episode to not feature a music score by Dudley Simpson since The Seeds of Doom: Part Six (1976) four years earlier.
ITV, the commercial TV competitor to the BBC, premiered Buck Rogers in the 25th Century (1979) directly opposite this episode, after a high-profile promotional campaign. ITV had previously attempted to compete with Doctor Who by scheduling science fiction in that slot before. Space: 1999 (1975) was only briefly successful in competing against Doctor Who, but when some ITV regions showed Man from Atlantis (1977) in late 1977, it impacted on Doctor Who's ratings. However, all of the ITV regions broadcast Buck Rogers in the 25th Century simultaneously, which decimated Doctor Who's ratings to all-time lows. Viewing figures continued dropping week by week. By week three, the series did something it hadn't done in 18 years: it fell out of the top 100 programmes for the week it was transmitted. Within two months, Doctor Who had fallen to a low of 3.7 million viewers, in stark contrast to the 16.1 million viewers it had achieved a year earlier when the ITV network was off air for several months due to strike action. This eventually prompted the BBC to move Doctor Who to a weekday timeslot for its next season in 1982.