ATP World Tour Finals: Roger Federer beat Milos Raonic 6-1 7-6 (7/0) in London

Roger Federer exacted revenge over Milos Raonic to make a winning start to his campaign at the ATP World Tour Finals in London.

Raonic beat Federer in the quarter-finals of the Paris Masters last week to book his spot alongside the Swiss at the O2 Arena as one of three debutants.

The first set was over before the Canadian had had a chance to settle into the match but he forced Federer to save a set point in the second before playing a poor tie-break to go down 6-1 7-6 (7/0).

In his second Group B match on Tuesday, Federer will play Kei Nishikori, a 6-4 6-4 winner against Andy Murray earlier, while Raonic will hope to open his account against the Scot.

Federer's fans flock to the O2 every year and there were hordes of them once again to welcome the 33-year-old back to London.

Federer, who has won this event a record six times, had welcomed the chance for another shot at Raonic and he wasted no time stamping his authority on the match.

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After winning points off 138mph and 141mph serves, Federer successfully challenged a delivery of 144mph and took advantage of the second serve to break for 2-0.

The second seed was timing the ball beautifully right from the start and Raonic looked a little shell-shocked as Federer raced to the first set in just 25 minutes.

The Canadian had landed 65 per cent of his first serves but his weaker backhand was being horribly exposed.

However, he began to do some damage with his forehand at the start of the second set and matched Federer despite his first serve going AWOL.

Federer could not find the same rhythm he had in the first set and Raonic's pressure paid off when he brought up set point in the 12th game only for his opponent to find a perfect serve.

Federer held to force a tie-break and Raonic never recovered from a poor start as his challenge ended with a whimper.

Fortunate

Federer admitted he was a little fortunate to come through in straight sets, saying: "I think I played really well for probably one and a half sets.

"When I had break point in the second set, he was able to save that. After that it became complicated. I don't know why.

"I had a couple of games where I was up 40-0, and both times he came back and got into the game, which was probably my mistake. But it made me uncomfortable.

"I started to play a bit more passive. He started to become a bit more offensive. I actually think he was the better player from that moment on and deserved the set more than I did."