|Planet of Origin:||Holst IV|
|Original era:||20th Century|
|Appears In:||The Mask of the Maharani|
|Portrayed By:||Michael Gough|
Gustav Holst was a Holstite from the planet Holst IV who was assigned to Earth as a covert spy in the early 20th century, where he worked under the assumed cover of an English musical composer and teacher. He encountered the Sixth Inspector in the Season 22 episode "The Mask of the Maharani". He was played by the English actor Michael Gough.
It was eventually revealed that his mission's real target was not Earth but the episode's eponymous Infinity Knight, and at the end of the episode he was allowed by the Inspector to continue both of his careers.
- The real-life Holst's classical composition "Jupiter" has been used as the main Inspector Spacetime title theme for most of the program's run, which was made the subject of a joke in "Mask" between The Inspector and his Associate Jeffrey Wells: "I quite liked that tune!" "Yes, I expect we'll be hearing it again."