Alpha Centauri (The Curse of Peladon)

Alpha Centauri was the Alpha Centauran delegate to Peladon.

Alpha Centauri first came to Peladon on the Committee of Assessment to review their petition to enter the Galactic Federation. It aided the Doctor in defeating Hepesh and Arcturus. (DW: The Curse of Peladon)

Fifty years later, Alpha Centauri was the Federation Ambassador to Peladon where it helped the Doctor defeat the plans of Eckersley and the renegade Ice Warriors. (DW: The Monster of Peladon)

Characteristics
Although it had a more feminine and high pitched voice, Alpha was neither male nor female; it was a hermaphrodite hexapod according to the Doctor. (DW: The Curse of Peladon) Nevertheless, the Doctor referred to it with masculine pronouns, and had a penchant for addressing it as "my dear fellow". (DW: The Monster of Peladon) 

Like most of its race, Alpha Centauri was a natural pacifist and a hypochondriac.