A new squadron of Cybermen arrive, kill Cutler, take control of the base, and order the Z-bomb to be disarmed.

[3] On the Monday before the programme was due to be recorded, he sent a telegram to the production team informing them that he was too ill to work.

Gerry Davis rewrote the script to explain the Doctor's absence (his sudden collapse) and gave his dialogue to other characters, most noticeably Ben.

[5][6] During the regeneration sequence at the end of the final episode, Patrick Troughton momentarily makes an appearance – uncredited – as the Second Doctor.

As such, it is included in a list of the twenty most wanted missing programmes (as drawn up by the British National Film Theatre) alongside the BBC studio footage from the Apollo 11 landings (which is currently held only in soundtrack form).

[7] Popular myth has it that the only surviving telerecording copy of the fourth episode was lost when loaned out to the children's programme Blue Peter in 1973 when they wished to use a clip from it in a feature on the tenth anniversary of Doctor Who.

Another department – BBC Enterprises – was still offering all four episodes for sale to foreign broadcasters until the end of the following year and would not have loaned out master negatives.

In 2000, BBC Video released the story on VHS, with episode four reconstructed by the Doctor Who Restoration Team using still photos, existing clips and the surviving audio soundtrack.

[8] ^† Episode is missing In 2009, Patrick Mulkern of Radio Times found the original Cybermen design like "usherettes from some kinky, futuristic moviehouse", but praised the character of Cutler and Hartnell's Doctor.

He praised the Cybermen and the "palpable tension", but felt that the regeneration was tacked on and not enough background was given to make Mondas believable.

[15] The Cybermen were conceived for The Tenth Planet by scientist and writer Kit Pedler and screenwriter Gerry Davis as a depiction of the ultimate outcome of biomechatronic and prosthetic technology in medical science.

The writer John Kenneth Muir has noted that Pedler and Davis had previously written about dystopian scientific themes, and would later collaborate on Doomwatch, a speculative fiction BBC TV drama series.

Muir suggests that the concept of the Cybermen may have been the inspiration behind a later popular science-fiction cyborg race, the Borg, which first featured in Star Trek: The Next Generation ("Q Who") in 1989.

[16] The writer Kevin S. Decker has evaluated the role of the Cybermen introduced in The Tenth Planet in terms of the traditions of continental philosophy, and considers that they have been deliberately crafted by Davis and Pedler to symbolise the Others in opposition to the human race.

Decker states that this sense of Otherness is achieved by Pedler's focus on the theme of "dehumanising medicine" by presenting a race of humans who have replaced most of their flesh and organs with cybernetic parts.

[17] Graham Sleight notes that The Tenth Planet was produced at a time when modern medicine was pioneering transplant surgery, lending a sense of topicality to Davis and Pedler's concept for malevolent cyborgs.

He also finds contemporary significance with the 1960s rocket programmes, and notes that the multinational makeup of the Antarctic base crew is particularly noteworthy, having no precedent in earlier Doctor Who stories.

[18] The introduction of the concept of regeneration in The Tenth Planet is noted as a landmark in the show's history, and it has been credited with establishing the longevity of the television series by ensuring the survival of the character of The Doctor.

The story was released on VHS in the UK in 2000 from BBC Video, with the fourth episode reconstructed by the Doctor Who Restoration Team using still photos, existing clips and the surviving audio soundtrack.

[25] It was mastered from 1960s vinyl records rather than original archive tapes, resulting in reduced dynamic range with crackle and rumble present throughout.