Dervish was an engineer for the Earth government before becoming Maurice Caven's second-in-command in his band of space pirates. Dervish was worried if they destroyed too many beacons, they would have the whole Space Corps chasing after them.
Dervish wasn't was as violent as Caven and when Madeleine Issigri found out Caven was going to murder his prisoners, begged Dervish for help. Dervish refused, and said he knew what Caven was capable of.
When Caven's plan to blackmail the Space Corps by blowing up Ta was foiled by the Second Doctor, Caven and the rest of the pirates made a quick escape in their Beta Dart. However, General Nikolai Hermack had Major Ian Warne destroy the Beta Dart, killing Caven, Dervish and the rest of their men. (TV: The Space Pirates)