Sir James Quinlan was the British Minister for Technology. He conspired with General Carrington to capture three aliens, hoping to have the political coup of making first contact; he used his power and influence to stymy UNIT's investigations, as they were an international body and not a British one. The Third Doctor was aware that Sir James was involved.
He phoned the Doctor and told him to come to his office, and that he'd tell him the "whole truth". However, Carrington had Reegan have one of the aliens murder Quinlan, in order to cover his tracks. (TV: The Ambassadors of Death)