Roger Federer is guaranteed to finish the year as world number one following his win over Andy Murray on Tuesday.

Federer held the world number one ranking from 2004 until 2008, setting a record breaking number of weeks in the top spot before Rafael Nadal finally ousted him with a brilliant 2008.

After Nadal’s Australian Open win at the start of this year many were once again predicting the demise of Federer but the Swiss has confounded them all and after winning the French Open and Wimbledon he’s back again at the top of the game.

Nadal closed the ranking points gap with a strong finish to the year to give himself a chance of overtaking Federer if things went his way in London this week. However the Spaniard has wilted with defeats to Robin Soderling and Nikolay Davydenko.

Federer described winning back the world number one spot as one of the greatest triumphs of his career. “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 is a wonderful achievement," he said. “The key this year has been playing well at the important moments, and staying healthy, especially after having a rough 2008.”

It’s the fifth time Federer has finished the year as world number one. The record is held by Pete Sampras who managed it six times.

Federer is now the bookies favourite to win this week. He's currently priced at 6/4 with Boylesports.