• Switzerland's Roger Federer serves against Serbia's Novak Djokovic during the singles final on the eighth day of the ATP World Tour Finals tennis tournament in London on November 12, 2012. (AFP PHOTO / GLYN KIRK)
  • For Federer, bidding for a hat-trick of Tour Finals titles, there was only frustration as he failed to take advantage of some dominant spells. (AFP PHOTO / GLYN KIRK)
  • Federer fizzed winners past Djokovic from all angles to take the first nine points of the match, breaking in the second game in the process. (AFP PHOTO / GLYN KIRK)
  • Roger Federer, 17-time Grand Slam champion is the most successful player in the history of the event, having won more titles and recorded more match wins than anyone else. (AFP PHOTO / GLYN KIRK)
  • Djokovic needed treatment after cutting his elbow while diving in vain to reach a Federer shot, but he regained his composure to win the match. (AFP PHOTO / BEN STANSALL)
  • Djokovic kept grinding away and eventually wore Federer down. (AFP PHOTO / BEN STANSALL)
  • Djokovic celebrated by thumping his chest and letting out a defiant roar. (AFP PHOTO / GLYN KIRK)
  • Serbia's Novak Djokovic (R) shakes hands with Switzerland's Roger Federer (L) after Djokovic won the singles final on the eighth day of the ATP World Tour Finals. (AFP PHOTO / GLYN KIRK)
  • Djokovic underlined why he will finish as the world's top ranked player for the second successive year in a row. (AFP PHOTO / GLYN KIRK)
  • The 25-year-old's brilliant display clinched his second triumph at the prestigious season-ending event and his first since 2008 when he won the title in Shanghai. (AFP PHOTO / GLYN KIRK)
  • Serbia's Novak Djokovic (R) poses with the winners' trophy. (AFP PHOTO / BEN STANSALL)
  • Novak Djokovic: world number 1, and champion of the 2012 ATP World Tour Finals. (AFP PHOTO / GLYN KIRK)