Alpha Centauri first came to Peladon on the Committee of Assessment to review their petition to enter the Galactic Federation. It aided the Third Doctor in defeating Hepesh and Arcturus. (TV: The Curse of Peladon) Five years after Peladon joined the Federation, when Princess Lixgaar of New Mars was taken to Peladon for safety, Centauri locked the Princess away in the tower containing the chamber of the Prisoner of Peladon. It didn't wish to keep this a secret from King Peladon, but was insisted upon by the Federation council to "conceal the truth".