Andy Murray qualified for the semi-finals and stayed on track to retain the world number one ranking with victory over Stan Wawrinka at the ATP World Tour Finals.
The Briton only needed one set to reach the last four, but beat the Swiss 6-4 6-2 to top the John McEnroe Group.
Murray extended his winning streak to 22 matches and goes through to face Milos Raonic on Saturday.
Novak Djokovic will take on Kei Nishikori in the other semi-final.
Djokovic also won all three of his group matches, and Murray must at least match the Serb's results at the O2 Arena to end the year at the top of the rankings.