Smith came home 0.216 seconds in front of Terol, who led a tight battle for the lead until the last eight laps.
BBC: Smith wins to lead championship
2.
The 18-year-old from Oxford started from pole and held off the challenge of Spain's Nicolas Terol, with previous championship leader Julian Simon third.
BBC: Smith wins to lead championship
3.
Basically, the title will be his should he finish ahead of Bradley Smith and 14th or higher if Nico Terol features in the top four.