Andy Murray was thrilled to be first out of the blocks as he opened his Barclays ATP World Tour Finals campaign with a three-set victory over US Open champion Juan Martin del Potro at London's O2 Arena.

The British number one had the honour of playing the first singles match at the prestigious eight-man event and began in style, winning the first five games before digging deep to seal a 6-3 3-6 6-2 triumph.

"It was a really good start," said the 22-year-old, who reached the semi-finals on his tournament debut last year.

"The start of the match was important. Me and Juan haven't played that much since the US Open so I kind of expected a little bit of a scrappy match maybe.

"He didn't start particularly well but after 5-0 I thought the standard was very good. We played some great points.

"Obviously I'm happy I managed to come back in the third because he was playing well."

The first set was a strange affair, with Murray saving two break points in the opening game before going on to take a 5-0 lead.

Del Potro took a medical time-out for attention to a nosebleed after the third game but he could not stem the flow of errors coming from his racquet.

Having saved two set points to avoid a whitewash, the Argentinian retrieved one of the breaks before Murray finally clinched the opener at the eighth time of asking.

However, the danger signs were there for the world number four and a sloppy service game at the start of the second set allowed his opponent to open up a 3-0 lead.

The topsy-turvy nature of the contest continued, Murray first breaking back after Del Potro's volleying again let him down only for the 21-year-old to power into a 4-2 lead with yet another break.

And three games later the world number five took advantage of his second set point to level proceedings.

Murray was on the back foot but seized his chance at the start of the decider, letting out a huge roar after breaking for a 2-0 lead.

And once again Del Potro eventually proved to be his own worst enemy, successive double faults giving Murray two match points and the Scot clinched victory with a crisp backhand winner.

Del Potro has now lost five of his six matches against Murray and said: "Against Andy, always the match is very tough.

"We play three sets in every tournament, every match.

"Today was a little strange but he played great tennis in the third set. He was a little lucky but you need the luck to win. And today it was with him."