The Light (1963: The Assassination Games)

The Light were a species believed to be the secret rulers of the universe, similar to the Illuminati in Earth conspiracy theories. They applied their genes in pre-natal drugs of other species to take over the unborn, and existed as a thousand species across a thousand worlds through time and space. Ace compared them to cuckoos. (AUDIO:  The Assassination Games) Aside from Light members proper, they also used Light Sleepers, sleeper agents that were activated in case of emergency. (AUDIO: Rise and Shine)

They arrived on Earth in 1850 and, seeing the British Empire as the greatest power in the world, took a foothold. However, by 1963, the United States of America and the Soviet Union had become the superpowers, and the Light had not infiltrated them. They developed the Starfire warhead project as a means of destroying the US, who would be expecting an attack from the Soviets during the Cold War. The Seventh Doctor helped to defeat them, but acknowledged that they were real and would want revenge. (AUDIO: 1963: The Assassination Games)

William Heaton claimed to be the last member of the Light left on Earth after the Starfire incident. (AUDIO: The Keep)