Biography
Alpha Centuri was on the commitee of assessment when Gemma Legato and Philip Armstrong petitioned for Earth to join the Galactic Federation, however he and the other members were skeptical due to the state Earth was in at the time. (CF: Consequences)
Centauri took part in a conference between various alien races. (DW: The Enemy Uncovered)
Centauri became a member of the Gallifreyan Union. (DW: Peace in Our Time)
Alpha Centauri agreed with the Doctor that the Poplne didn't attack the Bellonsions. (DW: Peace in Our Time, The Oncoming Storm)
Centauri was amongst the many aliens who attended the Doctor's funeral on Karn. (MOV: Doctor Who: Endgame)
Alpha Centauri first came to Peladon on the Committee of Assessment to review their petition to enter the Galactic Federation. They aided the Third Doctor in defeating Hepesh and Arcturus. (DW: The Curse of Peladon)
When they became ambassador, Centauri again helped the Third Doctor, this time to defeat the plans of Eckersley and a group of renegade Ice Warriors led by the Ice Lord Azaxyr. (DW: The Monster of Peladon)
Centauri was also present during the Eighth Doctor's efforts to recover the Diadem from Nic Reeceon Peladon in 3984. They attempted to repeal the Doctor's execution alongside his companion, Bernice, with little success. (DW: Legacy)