Roger Federer crushed old rival Rafael Nadal 6-3, 6-0 as the defending champion swept into the semi-finals of the ATP World Tour Finals on Tuesday. Federer went into the match knowing victory would guarantee his place in the last four after Jo-Wilfried Tsonga defeated Mardy Fish in the earlier Group B match. The Swiss star seized the opportunity with a brutal demolition of the world number two in just one hour on court at London's O2 Arena. The 30-year-old hadn't beaten Nadal since they met in the final of the ATP's season finale here last year, but he produced his most emphatic ever win against the Spaniard to ended a run of three successive head to head defeats. While Federer can relax in his final group game against Fish, there is no margin for error for Nadal, who needs to neat Tsonga on Thursday to make the last four. This was the 26th instalment of one of the great sporting rivalries and, while there wasn't a Grand Slam title at stake for once, Federer's masterclass made this just as memorable as some of their previous encounters. Nadal has often had the better of Federer, winning 17 of their matches including the last clash at this year's French Open final, but the meetings on hard courts have always been much closer affairs. Federer, aimig for a record sixth Tour Finals crown, arrived on a run of 13 successive wins which brought him titles in Basel and Paris and he was quick to impose himself with a dominant opening service game. The two heavyweights slugged away for the first five games until Federer suddenly produced the kind of sustained brilliance that has done for so many opponents in the past. Federer unloaded a stunning cross-court winner to rock Nadal back on his heels and then brought up three break points with a perfectly timed smash. That set the stage for one of the best rallies of the tournament as Federer worked Nadal around the court. The Spaniard fought gamely to stay in the point but eventually drove a backhand wide as the capacity crowd rose to their feet to acclaim both players. Federer had the bit between his teeth now and kept Nadal from threatening a comeback with some cleverly placed serves to close out the set. For the first time in the seven years they have been played each other, neither player was ranked number one after Nadal lost that spot to Novak Djokovic. Federer has slipped to fourth recently but the quality of his play in this mood remains unsurpassed. The 16-time Grand Slam champion continued to take the attack to Nadal in the second set and the Spaniard was unable to find the right response. A blistering exchange of ground-strokes in the first game ended with Federer producing a winner from a seemingly impossible angle to secure the break. It isn't often that Nadal looks shell-shocked on court, but he was beginning to wear an increasingly exasperated expression and Federer, scenting blood, went for the kill in the third game. Again Nadal had no answer as Federer blazed forehand winners at will to open up a 3-0 lead. Federer's serve was working beautifully and Nadal never threatened a fightback. The Spaniard was rendered impotent on his own serve as well and Federer broke again in the fifth game before serving out the match to complete a remarkable performance.