P is for... Primitives

The somewhat derogatory name given to the inhabitants of the planet Uxarieus by a group of colonists from 25th Century Earth. Initially hostile to the newcomers, they co-existed uneasily by bartering with each other. Sometimes the Primitives would abduct a colonist and they would have to be ransomed back by providing food. 

They painted their bodies using dyes made from rocks and roots and armed themselves with spears and knives. Their city lay close to the colony, but was in ruins. Most dwelt in a nearby underground complex ruled by a diminutive priestly caste which worshipped a powerful weapon. The Primitives were the devolved survivors of a once great technological civilisation, but now they used pieces of their ancient technology to adorn their bodies.

One Primitive assisted the colony's chief engineer, Jim Holden, who discovered that they had telepathic abilities. Despite this, the Doctor was at one point able to distract one of them with a disappearing coin trick.

A man named Norton turned up one day, claiming to be a survivor of another colony. He said that the Primitives had killed most of his people, who had also come under attack by giant lizards. He murdered Holden and his Primitive assistant before sabotaging the colony's power supply - making it look like the Primitive had attacked Jim first. This was because Norton was really an agent for IMC - the Interplanetary Mining Corporation - which wanted to exploit the planet's rich mineral resources and was prepared to kill to get them.

Found tied up in the ruined city by IMC guards, the Doctor's companion Jo Grant was kidnapped by the Primitives and taken to the underground complex - to be sacrificed to the weapon and its Guardian. The Doctor went to fetch her back.

Later, he was forced to return with the Master who wanted control over the weapon. The Guardian elected to sacrifice itself rather than see the device used for evil. The Doctor tried to save the Primitives and the priests, but without the Guardian to guide them they wandered aimlessly through the complex, and were destroyed when the weapon exploded. Some may have survived on the surface.

Played by: Pat Gorman, Derek Chafer, Les Clark, John McGrath, Stewart Anderson, Emmett Hennessy, Walter Turner, Mike Stephens. Appearances: Colony in Space (1971).

• The actors playing the Primitives are clearly wearing thin body suits, but they are supposed to be naked save for a loincloth. 
• Gorman, who appeared in the series regularly as an extra / monster performer (from The Dalek Invasion of Earth in 1964 to Attack of the Cybermen in 1985) played a colonist and an IMC guard as well as a Primitive in this story.
• A number of stuntmen also portrayed Primitives for action sequences, including Terry Walsh, Alf Joint and Dinny Powell.