Alpha Centauri, the timid one-eyed, six tentacled representative from the star system Alpha Centauri.  He was one of the Federation's delegates to Peladon, along with the Ice Warrior Arcturus's, and Martians Lord Izlyr and his aid Ssorg, as part of the committee of assessment to determine Paladin's request to become part of the Galactic Federation.

Even though Alpha Centauri is a stickler for protocol and legalities, she/he assisted in helping the Third Doctor unmask Hepesh (High Priest of Peladon) and Arcturus's' plan to stop the Peladon joining the Federation, and was thereby able to facilitate Paladin's accession the Federation (MMM). 

Fifty years later, when the Third Doctor returned to Peladon, Alpha Centauri was still their in the capacity as Federation Ambassador, and is able to vouch for the Doctor. 

The planet is in turmoil as the Federation is at War with Galaxy 5, and Peladon is the source for the mineral trisilicate which is needed for the war effort by the Federation. 

A disagreement breaks out between the miners and the planet's ruling class which halts production.  Alpha Centauri at the advice of Eckersley calls the Federation for assistance.

After the arrival of The Ice Lord commander Azaxyr, who puts the planet under martial law, Alpha Centauri assists the Third Doctor in exposing Azaxyr and Eckersley's plot to supply Galaxy 5 with the trisilicate. 

After the foiled plot Alpha Centauri reports that the war is over and then plays a role in the peace negotiations  (YYY).