Novak Djokovic capped a remarkable season with victory over Roger Federer to claim a record fourth straight ATP World Tour Finals title.
The world number one from Serbia won 6-3 6-4 in 80 minutes at London's O2 Arena.
Djokovic also made amends for defeat by six-time champion Federer in the group stage on Tuesday.
He ends the year with 11 titles including three Grand Slams, taking his total to 10 majors.
The 28-year-old has now won the season finale five times and surpasses Ivan Lendl's 1987 achievement, when he won his third straight Tour Finals title in New York.