Roger Federer started slowly but accelerated in a blur to take a giant leap towards the semi-finals of the ATP World Tour Finals in London.

Andy Murray had delighted the home crowd by racing to the opening set with flurry of fist pumps.

But Federer knows a thing or two about timing and peaking when it matters.

And he stormed back to secure victory 3-6, 6-3, 6-1 in just under two hours, leaving Murray feeling as blue as the brilliant azure court at London's o2 Arena.

The British number one appeared shell-shocked at the onslaught but must recover quickly.

He needs to beat Spain's Fernando Verdasco - beaten earlier in the day by Juan Martin Del Potro - to stand a chance of progressing to the weekend's knockout stages.

And even then he must hope the maths of games won and lost go in his favour in a tight group.

"It was a great atmosphere and I thought I played a great match," said Federer, whose popularity with the British crowd almost matches that of Murray.

"Andy was playing really well in that first set, I couldn't read his first serve and he made it very hard for me.

"When you are behind against the top players it's very difficult and I was a bit worried because I've lost so many three setters against him.

"But I picked up my game and when he dropped a bit, I took advantage. ?It's given me real confidence for my next match."