Novak Djokovic dedicated his Barclays ATP World Tour Finals title to his ill father after defeating Roger Federer to take the season-ending prize in London.
The world number one finished the tournament undefeated and picked up a cheque for $1,760,000 with his 7-6 (8/6) 7-5 victory over the man who had made the O2 Arena his own.
Federer was looking for a third title in a row and to extend his record to seven overall but he could not capitalise on good starts in both sets.
Djokovic has not matched his phenomenal year in 2011, when he won three grand slam trophies and 10 titles in total, but he has come closer than many might have expected and has won more matches in 2012 than he did last year.
The 25-year-old's performances this week have been particularly impressive given the worries over the health of his father Srdjan, who remains seriously ill with a respiratory condition.
Djokovic said: "It's been a very long year, a very long two years, but a very successful two years.
"I didn't really know how I would follow up after an incredible 2011, but I believed that I have to use the time where I'm playing the best tennis of my life and I'm winning grand slams, finally realise what I need to do to win the major tournaments.
"This was my time, my moment, and I needed to step in and really believe in my ability. So throughout the whole season I've had lots of success and had some disappointing losses at big events, in a couple of major finals.
"But all in all it was a fantastic year where I've had to face a lot of difficulties off the court as well.
"Especially coming into this tournament, having my father fighting his own fight for health gave me extra strength that I wanted to play for him in a way.
"That's one of the reasons I really gave it all every match, especially tonight. This was a title for him."
Djokovic added: "At a certain stage, it was very critical. We didn't know what tomorrow brings. But now he's much better and he's recovering. He's still in intensive care. I'm going to visit him tomorrow and see how it goes and try to bring a trophy with me and at least make him smile."