The Scotsman, who hadn’t made it to the last two of a tournament since his glorious triumph against Michael van Gerwen in the World Grand Prix, met the world number one again in Wigan.
This time the match went van Gerwen’s way, with the Dutchman hitting a nine-darter on the way to a 6-2 success.
But the run will encourage Thornton, who defeated Irish prospect Steve Lennon, challenge tour graduate Ryan Searle, John Bowles, Andrew Gilding, Mike De Decker and Robbie Green to reach the final.
“It’s been too long,” admitted the three-time major champion.
“I was very happy with my game all day and I hope this will be the first of many in the next couple of years as I bid to get back to my best.”