Thiem continues London run
Dominic Thiem overcame Alexander Zverev 7-5 6-3 to book his spot in the final of the ATP Finals for the first time.
World number five Thiem, who was struggling with illness ahead of Saturday's semi-final, was not at his fluent best throughout the contest but managed to pull off the big shots when required.
Defending champion Zverev, looking to become the 11th player to win the tournament more than once, started the better of the two but was unable to shake off his Austrian foe, who won the opening set 7-5 after his German opponent double faulted.
It was another close affair in the second set until Thiem made a crucial break of serve in game six to move 4-2 ahead, and the 26-year-old managed to win the set 6-3 to advance into Sunday's final.
The two-time French Open finalist will now take on Stefanos Tsitsipas in the final after the Greek produced a stunning performance to defeat Swiss legend Roger Federer in straight sets in the first semi-final.
Speaking after his win, Thiem said: "It is unreal to me and to beat the defending champion, a very good friend and unbelievable player - it is an unbelievable achievement. I'm very very happy."
James Mason grew up in Northumberland so is entrenched in both the football and golf scenes. A low handicap golfer, he also follows Newcastle United and predicts big things under Rafa Benitez.