The Lost World - Season 2 Episode 5 Divine Right

A riderless horse approaches our explorers, as if on a mission. When Roxton saddles up, the horse carries him to a mountain tribe, who welcome him as their king. Roxton tries to decline, but when the royal advisor, Balar, tells him that if he's an imposter; he shall die, Roxton reconsiders. Using the horse, Roxton tries to warn his friends. Balar has the horse followed and they are captured. One of the customs of the tribe is to sacrifice a virgin to appease a monstrous dragon, but Roxton saves the young woman and steps right into Balar's trap. The only way to stop the dragon now is for the rightful king to hunt it down and kill it.