* Federer ends year on a high
* Swiss equals feat of Lendl and Sampras (Adds details)
Roger Federer sent a timely reminder to Rafael Nadal on Sunday, out-gunning the world number one to win the ATP World Tour Finals with an irresistible display of attacking tennis.
Federer, overshadowed this season by the phenomenal Nadal, won 6-3 3-6 6-1 in front of 17,500 fans at London's O2 Arena for a record-equalling fifth title at the year-ending finale, matching the feat of Ivan Lendl and Pete Sampras.
Nadal, who won this year's French Open, Wimbledon and U.S. Open titles to knock Federer off the top of the rankings, looked jaded after his epic semi-final against Andy Murray on Saturday and the Swiss seized his chance in style.
Federer fired down 32 winners in the one hour 37 minute contest to Nadal's 11 as he beat the Spaniard for only the second time in two and half years.
Nadal now leads 14-8 in their series dating back to 2004 but Federer's form since his shock defeat by Tomas Berdych at Wimbledon suggests the 24-year-old will be challenged hard for the sport's majors again next year.
In going through the round-robin tournament undefeated Federer also added $1.6 million to his considerable bank balance, although notching another victory over his great rival, and regular nemesis, was satisfaction in itself.
The 16-times grand slam champion roared with delight as he looped a forehand on to the baseline and, after a slight hesitation, Nadal opted not to challenge the call and began walking to the net to shake hands.
For the time since 1986 the world's top two players in the ATP rankings contested the final match of the season -- a fitting end to a tournament that attracted 250,000 fans over eight days to London's Docklands.
Though the match lacked the drama of their previous one in London -- Nadal's unforgettable 2008 Wimbledon final defeat of Federer -- it still provided a feast for a sell-out crowd as both players traded blows.
Nadal had the first sniff of a chance at 3-3 when he had Federer down 0-30 on serve but he was helpless as the Swiss reeled off four perfect points.
In the next game, Federer earned a break point with a forehand winner and converted it when he rolled a backhand beyond the reach of Nadal.
In what seemed like the blink of an eye, the Swiss had moved a set ahead but Nadal, playing in the final of the season-ender for the first time, levelled the match after breaking Federer's serve in the fourth game of the second set.
Predicting a winner at that stage looked impossible but Federer struck the decisive blow to move 3-1 ahead in the decider when Nadal hit a tired-looking backhand wide.
Nadal got to deuce on the next game but Federer slammed the door shut with an ace to move 4-1 ahead and there was no way back for the Mallorcan.