After five laps he had a 1.6 second lead and in two more laps had pulled that out to two and a half seconds over Espargaro and Terol.
Behind those two, Smith was in a dog-fight with Efren Vazquez and Esteve Rabat for fourth place.
With nine laps gone, Terol had displaced Espargaro in second but was making no impression on Marquez, who had a three and a half second buffer which he stretched lap by lap.
With seven laps to go, Espargaro got inside Terol at Doohan Corner and was in second as they arced over the top of the Southern Loop while further back Smith got in front of Rabat and Vazquez for fourth.
Going onto teh final lap, Marquez had stretched his lead out to 5.7 seconds while Espargaro had got a 4.9 second break over Terol.
The battle for fourth was taken by Vazquez from Bradley Smith.
As a result of his win, Marquez stretched his championship lead from three to 12 points over Terol with Espargaro another five points behind.
The points positions are: Marquez, 272; Terol, 260; Espargaro, 255.
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