Derek (Survival)

Derek was a human who in 1989 was transported to the Cheetah World by a Kitling.

Biography
Derek found Midge and Shreela Govindia, two other humans who were being hunted by the Cheetah People. Ace helped them try to catch a Cheetah Person but she failed. Instead they caught the Seventh Doctor and Sergeant Paterson. When Ace became infected with the Cheetah Virus she helped them get home. Derek was grateful and said, "Thanks Doctor, thanks Ace," unlike Paterson who just walked away. (TV: Survival)

Behind the scenes

 * Although he survived in the television story, in the novelisation he was killed by Midge after they returned to Earth from the Cheetah World.