Thornton's first professional title came in the Central Scotland Open in April 2007, beating Mike Veitch in the final. He also won the Scottish Masters by defeating Ross Montgomery. He failed to make it through the qualifying event for the 2008 World Championship, but did make it to the televised stages of the 2007 Winmau World Masters in the same weekend. Thornton then beat Co Stompé, BDO world champion Martin Adams, and Atkins to reach the final. He managed to avenge his defeat by Fitton at the 2005 Lakeside World Championship to claim his first major title by 7 sets to 5 and win the £25,000 first prize and also a place in the 2008 World Championship.