LARRY Mize was laughing all the way to the bank after completing an astonishing runaway victory in the third Johnnie Walker World Championship - a tournament he did not even qualify to play in. A sparkling final round of six-under-par 65 over the Tryall Club lay-out gave the American a 10-shot victory over Fred Couples in the US$2.7 million pre-Christmas bonanza in the sun. Mize's 72-hole aggregate of 266 - 18-under-par - was 15 shots better than Couples' winning score in 1991 and eight less than Nick Faldo a year ago. It was the second biggest winning margin of the year, surpassed only by Nick Price at Sun City in the Million Dollar Challenge a fortnight ago. The hallmark of Mize's game was his consistency, borne from a new belief in his swing which he has been working on with golfing guru David Leadbetter for the past two years. ''David has been telling me to trust in my swing. That is what I have done this week. I have tried to pick up my tempo and be more aggressive,'' said Mize, who was ranked 41st in the world at the start of the tournament. From tee to green, Mize was impeccable, while his putting was solid and, at times, inspired on the grainy greens. In shooting rounds of 67, 66, 68 and 65, the 35-year-old from Augusta recorded just six bogeys. Those rare blemishes were offset by a total of 24 birdies. ''Everything came together for me this week,'' said Mize, who collected a cool US$550,000 for his triumph. ''To beat a field of this calibre is an accomplishment. It has to rank as some of the best golf I have ever played. I won't soon forget it.'' Mize acknowledged that he was fortunate to be in the tournament at all, having failed to qualify automatically. His path into the 28-man field came courtesy of Australian Greg Norman, who withdrew three weeks ago citing exhaustion. Mize was then invited by the International Advisory Committee. It was an irony not lost on Mize. In 1987, Mize had holed an outrageous chip at the second hole of a sudden-death play-off to win the US Masters at the expense of Norman. It remains his only major championship success. ''I'm very grateful to Greg. I probably should give him something for Christmas,'' said Mize, who had no hesitation in accepting the invitation to Montego Bay. Mize had began the day with a three-stroke lead from Scot Colin Montgomerie, the only realistic contender. But Montgomerie, requiring a solid start, did not get one. There was a two-shot swing in Mize's favour at the 169-yard, par-three third where the American holed from 10 feet for birdie and Montgomerie three-putted for a four. Mize's advantage was increased by another two at the fourth when he made three and Montgomerie missed from two feet for a five. With the contest effectively over, Mize was able to relax. His third birdie of the day at the sixth enabled him to turn in 32 and he rolled home further birdies putts at the 12th, 14th and 17th. Montgomerie never recovered from his early setbacks. Turning in 40 he had surrendered second place and eventually finished with a 74, leaving him in fourth position on 278. ''That was the worst nine holes I've played this year,'' said Montgomerie. ''It's a shame it had to happen in the last round of the year. I tried my darndest to get it back, but it just wouldn't happen for me.'' While Montgomerie had spent most of the day going in reverse, Couples soared up the leaderboard with a staggering 64 - the best round of the week. After a double-bogey seven at the fourth, Couples admitted he was ready to go home. He said: ''I just kind of said: 'Let's finish up and get out of here'.'' He made birdies at the next two holes, added another at the ninth and then made five birdies in a row from the 11th. Back in the clubhouse, Couples waited to see if his 276 aggregate would be good enough for second place. Germany's Bernhard Langer needed a birdie at the last to pip him. But not only did Langer fail to make the three he required, but he three-putted to finish with a 69, which left him third. Couples, with aggregate of 276, finished second after Bernhard Langer's three-putt on the last left the German third. Couples won US$300,000 and Langer US$200,000.