Hyperon

This topic might have a better name.

[The planet is called Hyperon not Hyperion, according to the audio, subtitles, and script of the episode.

Talk about it here.

You may wish to consult Hyperion for other, similarly-named pages.

Hyperon was a planet which sent a fleet of war rockets to intercept a Dalek invasion of Venus in the Space Year 17000, as the Fourth Doctor recounted to Davros. (TV: Genesis of the Daleks)