The Bannermen were persecuting the Chimerons to the point of extinction. They had killed most of the Chimerons on the planet Chimeria but one escaped along with an unhatched egg. Gavrok, the leader of the Bannermen, pledged to exterminate them all, and pursued the Chimeron Queen Delta.
A bounty hunter on Earth told the Bannermen of the location of Delta and the warfleet descended on Wales. The Bannermen were defeated by the seventh Doctor, Mel, some local people, and a Chimeron child. The Bannermen were bound and taken prisoner by Delta, the Chimeron Princess and localman Billy to be taken to court and held to account for their crimes.