Dustin Johnson claimed the biggest victory of his career thus far, after producing a brilliant finish to fend off the challenge of Ian Poulter and Graeme McDowell at the WGC-HSBC Champions in Shanghai.

The 29-year-old American had entered the final round with a three-shot lead, but saw that advantage evaporate after just two holes on Sunday. However, he would react to that change of complexion superbly, with a stunning barrage of low scoring – playing his closing six holes in five-under – to post a final round of 66 and a claim a three shot victory over defending champion Ian Poulter at Sheshan International.

Graeme McDowell completed that final three-ball on Sunday, and the 2010 U.S. Open champion, like Johnson and Poulter, would settle for a closing round of 66 to secure sole-possession of third. Sergio Garcia would finish in fourth, after a course-record equalling round of 63 took him to 18-under, six shots behind Johnson’s winning total.

It was a special day for Johnson, but it started in rather ignominious fashion. He would three-putt for a bogey on the first hole, with Poulter opening with two birdies of his own to claim a share of the lead. McDowell started even more impressively, with three successive birdies of his own to also join that tie at the top.

It looked as though Poulter and McDowell would ultimately duel it out for the title, but Johnson bounced back with consecutive birdies at the eighth and ninth to tie the Englishman. The 37-year-old Poulter, who claimed his second World Championship I Shanghai last year, would edge ahead again after a birdie at the 12th. Johnson, however, would stand up to the mark, and tied the Ryder Cup star once again, after a birdie at the 13th, before they both traded birdies on the 14th to leave them tied at the summit with four holes to play.

A defining moment would occur on the 15th, with Johnson reclaiming sole possession of the lead after Poulter made bogey. However, the closing holes of Sheshan are ideally suited for a comeback, with a driveable par four and a reachable par five ahead.

That reachable par four is the 16th, but all three players ended up short of the green after their tee shots. However, in this case, the importance of Johnson’s prodigious length was illustrated, as he left himself just ten yards short of the green after hitting an iron off the tee. From this position, he would dramatically chip-in for eagle and take full control of the tournament.

Ian Poulter did manage to birdie the 16th, leaving him just two shots behind the American with two holes remaining.

The South Carolinian born player would quickly dispel any possibility of late drama, with a stunning tee shot on the par three 17th left him with just five feet for birdie. He would convert that putt to ensure of himself a three shot lead on the 18th tee.

Yesterday, Johnson found the water off the tee on the final hole, which ultimately cost him a double bogey. There was no danger of a repeat occurring today, as he sensibly took an iron off the tee with a three shot cushion on his side. He would lay up with his second shot, before settling with a closing par that saw him clinch his first World Golf Championship title.

Winning those co-sanctioned event saw Johnson claim his eighth title on the PGA Tour, and his first on the European Tour. With his coach Butch Harmon long being proponent of his players travelling around the world to play, this victory establishes Johnson as a successful international player.

“I didn't get off to the best start and Poulter and McDowell got off to great starts and put a lot of pressure on me, but I am swinging well and putting well so I thought just stick to my game plan and play the golf course how I want to play it and it's going to come”, said Johnson in his winner’s press conference.

”I played really well the last few holes on the front nine and then had a great back nine. The guys made it really interesting but I just played really well coming down the stretch.

”The last few holes here you can make some birdies. It was a lot of fun out there; it was a good match from both of them. They put a lot of pressure on me but I am really proud of myself and the way I handled it.”

Dealing with that final round pressure in big events hasn’t always come easy to Johnson, who dramatically threw away a three shot lead in the opening holes in the 2010 U.S. Open at Pebble Beach. Graeme McDowell took full advantage to win that Championship, as Johnson struggled to a final round of 82.

However, there would be no final round disaster from Johnson, as he reflected on the importance of maturity and patience when tackling the challenge of a final round with the lead.

“It takes a while to learn that (maturity and patience),” added Johnson, who has won in each of seven seasons on the PGA Tour. “I wish I would have had some of that a few times a few years ago, but you learn from your mistakes and try to get better from them and I think I showed a lot of patience and a lot of discipline with clubs I picked and shot selection.

”This is probably my biggest win and hopefully there are better things to come.”

Ian Poulter moves up to fourth on the Race to Dubai, with Graeme McDowell cutting Henrik Stenson’s lead at the top down to less than €150,000 with two events remaining of the ‘Final Series’.

“I guess it was a good defence,” said Poulter. “Obviously a little disappointed not to put my hands back on the trophy, but 15 birdies and an eagle at the weekend is some pretty good golf.

”It's exciting for the next few weeks ahead, and obviously it's some good points on the board for Ryder Cup and Race to Dubai.

”I'm in great form and I really am playing well. The work I've done, obviously leading up to this run of tournaments has really worked and I couldn't be hitting it any better right now and obviously rolling a few putts in.”

U.S. Open champion Justin Rose finished in fifth, with Rory McIlroy and Canada’s Graham DeLaet in a tie for sixth at 15-under. Although he fell out of contention after leading after the opening round, McIlroy has accomplished one target, after ensuring of his place in the season ending DP World Tour Championship in Dubai.

However, it is Dustin Johnson who reigns in Shanghai as the United States complete a clean sweep of the World Golf Championships in 2013.