Trevor Sigma

Trevor Sigma, the 'Sigma' designated that he was from a planet other than Terra Alpha.

Biography
Trevor was a citizen of Earth who came to Terra Alpha to investigate the colony planet, but when he did he had to stay for 10 years. Trevor Sigma distracted Joseph C so the Seventh Doctor could talk to Helen A. (DW: The Happiness Patrol) He worked as the Offical Galactic Censor.