Swiss star Roger Federer has been crowned ATP World Tour Champion for the fifth time after defeating British favourite Andy Murray 3-6, 6-3, 6-1 on Tuesday evening to inch closer to a place in the semi-finals of the Barclays ATP World Tour Finals at The O2 in south-east London.

"These best of three set matches are tough, especially when the best players play each other," said Federer. "Whoever has the momentum, he can swing freely. The other guy has to be careful. That's why the beginning of sets are crucial. Of course, I had my doubts I was going to come through after having lost so many times in three sets against him. It feels good, but more than that, I think this is more the night to celebrate No. 1 than celebrate the victory over Andy really."

The 27-year-old Federer reclaimed the year-end No. 1 spot in the South African Airways 2009 ATP Rankings after being dethroned by rival Rafael Nadal last year. The 15-time Grand Slam champion, who was ATP World Tour Champion from 2004-07, joins Americans Pete Sampras (six times from 1993-98) and Jimmy Connors (five times from 1974-78) as the only players with five or more year-end No. 1 finishes in the history of the South African Airways ATP Rankings (since 1973).

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Federer is also only the second player in the history of the South African Airways ATP Rankings to have held, lost and then regained the ATP World Tour Champion title following Ivan Lendl, who finished No. 1 between 1985-87, came second behind Mats Wilander in 1988 and reclaimed the top spot at the end of 1989.

"Obviously, that was one of my big goals for this season," said Federer after the match. "And it's one of the greatest performances I think I've achieved. Seeing also what happened off the court: getting married, having twin girls, reaching all four major finals. Playing so well at the most important moments, it's been the key this year, and staying healthy. 

"Especially after having a rough 2008, coming back this year and being able to dominate and play at the top when the depth in tennis is so, so great at the moment. I think it's a wonderful achievement."

Victory for Federer went some way to avenging the round-robin defeat he suffered to Murray at the season finale in Shanghai last year, which meant the Swiss failed to qualify for the semi-finals for the first time in seven appearances at the year-end championship.

Roland Garros and Wimbledon reigning champion Federer is not assured of his place in the semi-finals just yet, though, as he, Murray and del Potro could all tie with a 2-1 match record in Group A – should del Potro defeat Federer and Murray beat Fernando Verdasco on Thursday.

To guarantee his place in the semi-finals, Federer must avenge his US Open final defeat to del Potro, while Murray needs to beat Spain’s Verdasco and hope that Federer defeats del Potro. Debutant Verdasco also has a slight chance still to qualify for the semi-finals, but would need to defeat Murray in straight sets and hope that Federer dismisses del Potro in the same fashion.

In the pair’s 10th meeting, and fourth this season, Murray rocked the 17,500 capacity crowd at The O2 as he rallied from an early break deficit to clinch the first set against Federer. Federer largely targetted the Murray backhand, especially under pressure, but the Scot was equal to the task and patiently soaked up the barrage before earning an error from Federer to decisively break for a 4-2 lead.

Federer’s tactic reaped better rewards in the second set, though, as he capitalised on a lack of first serves from Murray to take an aggressive game plan to the Dunblane native. In the sixth game the Swiss worked the Scot’s backhand over again until he created space for an off forehand winner to clinch a 4-2 lead before going on to level the match.

Murray continued to struggle with a low first-serve percentage in the deciding set and Federer made him pay, keeping up constant pressure on the 22 year old and welcoming the errors that came in reply. The Basel native won the final six games of the match from 0-1 to seal victory after one hour and 57 minutes and cut his head-to-head deficit against Murray to 4-6. He also defeated Murray in their last meeting in the semi-finals of the Western & Southern Financial Group Masters to end a streak of four Murray wins against him.

“It was a great effort to win a set serving like that,” said Murray, who committed eight double faults in total. “The first serve went in, I obviously won a lot of free points. It was probably the most double faults I served in a match maybe this year. So didn't serve well.

“I didn't play well. It happens sometimes,” confessed the Scot. “I didn't play well and I made mistakes. “It's difficult against him, if you miss so many first serves then you put yourself under a lot of pressure. Maybe I made more mistakes than normal, but I just didn't play well.”

Murray also lamented a lack of match practice in the past three months. Following the Davis Cup in September, he was sidelined with a wrist injury and did not compete again until lifting his sixth trophy of the year at the Valencia Open 500 (d. Youzhny) in October.

“The one thing that's been a problem for me since I came back was I played well-ish [sic] first set of the matches. Then when the adrenaline wears off, I don't know, there's not quite the same spark in the legs that there was at the start of the year. I've had let downs in a lot of matches. I've let guys back in the match straightaway, early in the second set  And that's something that I was doing really, really well when I was playing a lot at the beginning of the year. When I was getting ahead, I was not giving guys chances to come back into the matches.”