From TARDIS Index File, the free Doctor Who reference.
Bigon was a Greek philosopher. He and other Greeks were abducted by Monarch on his fourth visit to Earth and converted into androids. Bigon was promised that he would rule over Europe once the planet had been conquered, but he rejected this offer, as he believed that democracy was the best form of government. He aided the Doctor in defeating Monarch, and the androids decided to look for another planet on which to settle. (DW: Four to Doomsday)