Okdel L'da

Okdel was the leader of the Silurian triad of Wenley Moor, which included Morka (Young Silurian) and K'to (Silurian Scientist). He had developed a relationship with Dr John Quinn. The Doctor convinced him that the Silurians could share Earth peacefully with Mankind. When he realized that Morka was trying to wipe out humanity with a virus, he freed the Doctor and gave him the means to find an antidote. He was then killed by Morka. (DW: Doctor Who and the Silurians)

Behind the scenes
Okdel was not named on-screen, only in the novelisation and in MA: The Scales of Injustice. He was listed as Old Silurian in the credits.