High Minister Defron was a Zerugian who organised the negotiations and brought both sides together. When first meeting the Tenth Doctor and Martha, he believed they were Galactic Alliance observers. He explained to them that Castle Extremis was in the Sarandon Passage. Anthium was on one side and Zerugma on the other. When Secretary Chekz was killed, he was astonished to have a murder during the conferences.
As apparent Galactic Alliance observers, Defron had the Doctor and Martha present at the further conferences and the final handing over of Castle Extremis to the Galactic Alliance in case of any problems or awkward questions. At the conference when General Orlo took over, he was surprised to learn that they weren't actual members of the Galactic Alliance council. (PROSE: Martha in the Mirror)