The Android Invasion
Marshal Chedaki was a Kraal military leader. He worked alongside Chief Scientist Styggron as they prepared for an invasion of Earth. He was critical of the scientist’s incessant experiments, hoping to speed up the time frame for the conquest. Styggron mollified him by explaining that he wanted to continue the testing of the Kraal androids for future invasions, after Earth had been colonised.
Chedaki also presented to Styggron fears that the Fourth Doctor might turn the androids against the Kraals. The scientist created an android of a UNIT soldier, which he destroyed as a demonstration of his power over the things he created. Chedaki was critical of a “foolish experiment” involving an android of Sarah Jane Smith, but approved of Styggron’s initiative to test the Kraal virus on the real Sarah.
Styggron planned to have the androids release the virus on Earth. Chedaki would then arrive on the planet with the Kraal fleet and take control. However, the androids were disabled by the Doctor’s use of radar dishes and Styggron was killed by the virus. (The Android Invasion)
Behind the scenes
For the part of Marshal Chedaki, it would appear that Roy Skelton used a variation on his “Zippy” voice from the children’s television series Rainbow.