Saint George alternative history

There once was a town that was under the regime of a dragon. That dragon shook the city whenever he pleased and ordered once a week someone who could eat. To choose the next victim dragon people to a sweepstakes at the center of the square. In the village lived a beautiful princess, who had the misfortune of being chosen for that sweepstakes. Saint George, a knight learned that a village was being dominated by a dragon and proposed to go help those poor people.
The next day the knight went to the dragon's cave where he was waiting.
When Jordi came the battle began. After a tough battle the dragon gave up and Saint George made a pact with him. If the dragon joined him, could dominate the world. The dragon didn't thought a moment and went to Saint George to destroy and plunder the villages.