Roger Federer began attempts to win a record seventh title at the ATP World Tour Finals with a comprehensive straight sets win over Milos Raonic.

Federer avenged his defeat to Raonic at the Paris Masters with a conclusive 6-1 7-5 victory at the O2 Arena in London.

The world No.1 stormed into an opening set led in just 25 minutes and despite Raonic, on his ATP Finals debut, improving in the second Federer prevailed in the tie-break 7-0.

With the overwhelming back of the O2 Arena crowd, Federer marched into an early lead, converting the third of three break points in the second game as Raonic succumbed to early nerves.

The Canadian had disposed of the 17-time grand slam champion indoors in Paris a fortnight ago in his only victory in the pair's seven meetings but looked overwhelmed on his Tour Finals debut.

Though a 145mph serve helped Raonic register his first game of the match it was the only glimmer a decisive Federer allowed him as a string of forehand errors opened up a double break.

And in just 25 minutes the Swiss has the opening set wrapped up as he closed in on a first round robin victory.

Raonic provided a greater threat early in the second set, reeling off successive forehand winners though he was unable to take either break point chance that came his way.

The Federer serve was growing increasingly ragged as Raonic came forward while he began to show greater assurance on his own serve however another missed break chance was indicative of his evening's work.

With Federer edging towards a second set tie-break Raonic brought up a first set point but skewed a backhand return wide, allowing the six-time champion out of jail.

It would be an opportunity Raonic would come to regret taking as Federer produced seven successive points to win the resulting tie-break and start his campaign in the English capital in ideal fashion.