Christopher Jennings

 was a scientist who worked with Kalu as a postgrad student. He was helping to make a chronon bomb. He had devolved as part of the experiment into an ancestor of Humans, when he became corporeal after the experiment. In Interstitial time he told Tegan Jovanka that he caused the problems. He wanted to make Kulu sees sense. He was stabilised when he entered the TARDIS. (AUDIO: Interstitial)