Andy Murray celebrates winning start to ATP World Tour Finals

ANDY Murray kicked off the ATP Tour Finals in emphatic style, defeating US Open champion Juan Martin Del Potro in three sets at the O2.

ONE DOWN: Andy Murray beats Juan Martin Del Potro in ATP Tour Finals opener at London's O2 (Getty Images)

The Scot has enjoyed his best season to date, becoming the first Brit to reach world number two.  And he made the ideal start to his last tournament of the year, eventually coming through 6-3, 3-6, 6-2.

Argentinian Del Potro has also had a season to remember, lifting his first grand slam title at Flushing Meadows in September. But Murray has always had the mental edge over the world number five and extended his head to head record to 5-1 with the win.

It was never easy for Murray with Del Potro's depth on his groundstrokes too much for the world number four to handle at times.

But the Scot has weapons of his own and wasn't allowing his opponent a single free point on serve - something the 6'6" Argentine has become accustomed to.

And Murray admitted denying his opponent any free points was the key to his win.

"It was always going to be a tough match today," said Murray.

"I've played him four or five times and every one has been really tough so I knew what to expect. But I felt like I played really well today and started great.

"He came back into it in the second set but thankfully I stayed tough in the third set to see it out.

"He got a lot of free points on serve in that second set but I knew I had to stamp that out and that was the difference in the decider really."

Having reached the semi-final stage last year, the fired-up Scot is clearly keen to end his season on a high again this year and raced to a 5-0 lead with barely 20 minutes on the clock.

And although the British number one was the overwhelming crowd-favourite in London, there were a few ironic shouts of support when Del Potro finally got off the mark, holding his serve at the third attempt.

The cheers were quickly muted when the Argentine proceeded to break Murray's serve for the first time to bring the score back to 5-2, before holding his own again to return to within two games of the Scot.

But Murray was in focussed mood and needed just five points on his next game to seal the first set.

There was a sense that the Argentine was beginning to find his feet at the end of the first set and so it proved. At the beginning of the second, he smashed his way through his opening service game before punishing a lax Murray game to go 2-0 up.

The momentum swung briefly back in the Scot's favour as he broke back to go 3-2 behind but Del Potro immediately restored his advantage before efficiently serving out the set.

A pumped up Murray jumped out of his seat for the start of the final set and with a fist pump and a ‘come on!', the Scot clinched an early break before consolidating it to go 3-0 up.

The Argentine rallied and fought his way back into the set but he couldn't work a break point on his opponent's serve as Murray classily progressed to a 5-2 lead.

Finally, the pressure proved too much for Del Potro in the ultimate game as he threw in two double faults on the way to defeat.