Medok

Medok was an inhabitant of a human colony secretly ruled by Macra.

Biography
Medok discovered the existence of the Macra but was believed by the other colonists to be insane. When attempting to convince the Pilot, he caused some confusion by insinuating that the Macra were insects, and his claims were dismissed. (PROSE: Medok) However, he succeeded in alerting the Second Doctor to the threat.

When Medok was captured, he was sent to the gas mines to work. He was killed by a Macra when he tried to escape. (TV: The Macra Terror)

Behind the scenes

 * In Ian Stuart Black's novelisation of the story, Medok survives his encounter with the Macra in the mine, and emerges just in time to witness the Doctor and his companions departing in the TARDIS — deciding there and then never to breathe a word of what he has just witnessed.