Megara One

Megara One was the name given by the Fourth Doctor to one of the two Megara, the other being Megara Two. (PROSE: Doctor Who and the Stones of Blood)

When Romana I was kidnapped by Cessair and taken captive aboard her ship, the Megara were alerted to her presence after the Fourth Doctor went to rescue Romana. They put the Doctor on trial and sentenced him to execution. Through the trial, the Doctor was able to get the Megara to recognise Cessair, and they turned her to stone. (TV: The Stones of Blood)