Novak Djokovic produced another scintillating performance to beat Stan Wawrinka at the ATP World Tour Finals.
The world number one recovered from losing the first two games to win 12 of the next 13 in a 6-3 6-0 win.
He has not lost at the O2 Arena since 2011 and is now unbeaten in 29 matches indoors.
Djokovic remains top of Group A with his final round-robin match against Tomas Berdych to come.
The Serb will guarantee the year-end number one ranking with another win on Friday, and it is hard to see who can stop him claiming a hat-trick of ATP World Tour Finals titles on Sunday.
"Obviously Stan wasn't feeling his best today," said Djokovic. "He made a lot of unforced errors, a low percentage of first serves in.
"On my side, I just played very solid from all over the court. I think I covered the court very well, got a lot of balls back, mixed up the pace, got him off the comfort zone. That's something that was part of my game plan.
"After I lost the first two games, obviously I didn't start so great. I thought he played very well the first two games. But I wasn't frustrated, I kept my calm.
"After that, it was a really amazing performance."