From TARDIS Index File, the free Doctor Who reference.

David Winton
Also known as:
Race:	Human
Home Planet:	Originally Earth Uxarieus
Home Era:	Mid 25th century
Appearances:	DW: Colony in Space
Actor:	Nicholas Pennell

David Winton was a colonist in the human settlement on the planet Uxarieus. He was the chief political rival to the leadership of John Robert Ashe, strenuously arguing for the colonists' departure to another, more habitable planet. However, once the forces of the Interplanetary Mining Corporation arrived and threatened to compel the colonists off the planet, Winton became fiercely protective of his new home. He led an assault against the IMC ship, and in general argued for a more militaristic response to the threat than Ashe was willing to undertake.

After Ashe sacrificed himself to ensure the colony's survival, Winton became the leader of the group. (DW: Colony in Space)