Kelvin (The Infinite Quest)

Pilot Kelvin was a man in the human infantry fighting against the Mantasphids. He broke into the hive, confronted the Mantasphid Queen and told the fleet of her location. Realising he would die too, he helped the Tenth Doctor arrange a truce between the humans and Mantasphids and became the human ambassador to the Mantasphids. (DW: The Infinite Quest)