The Irishman, who fought off strong challenges from Scotland's Andrew Coltart and the Yorkshireman Howard Clark, shot a final round 68 to finish on 281, seven under par with Coltart on 284 and Clark on 285.
Later Walton paid tribute to his coach, Bob Torrance, who spent 18 hours with him last week advising him to widen his swing. "I owe Bob a lot," Walton said . "I've felt a different player this week. But my victory was never as easy as the final scores suggested because Andrew pushed me right to the final hole."
Because of gale-force winds, only half the third round was completed on Sunday and Walton played 30 holes yesterday in what he agreed was one of the longest golf days of his life.
At the end of the third round, he was second on 213, one shot behind Clark and one ahead of Coltart and Phillip Price, of Wales. Price soon fell away but Coltart went out in 34, led with nine holes to play but had a double bogey six at the 11th, allowing Walton to take the lead.
The Irishman, whose only previous Tour victory was in the 1990 French Open, birdied the 12th, 13th and 14th holes, and at this point led Clark by three shots and Coltart by four. But the Scot refused to give up hope, birdied the 15th then had a brilliant eagle three at the 17th to go only one shot behind.
Coltart, however, could manage only a bogey five after going over the back of the 18th green in two, while Walton finished with a flourish by hitting a nine iron to 12 inches for a birdie three and the £50,000 first prize.
n Nick Faldo had a final-round 68 to finish joint fourth - his fourth top-five finish since winning at Doral six weeks ago - in the Heritage Classic at Hilton Head Island, South Carolina. Bob Tway, of the United States, won at the second extra hole.Reuse content