Anders Hansen made a final-round charge with a 66 to share second place with Bradley Dredge and Richard Finch at 15-under-par 273. Local favorite Emanuele Canonica was one shot further back at 14-under-par 274.
Webster had come close to his maiden win several times before, including a playoff loss to two-time U.S. Open champion Retief Goosen at the 2001 Telefonica Open de Madrid. Webster was given another chance this week at Castello di Tolcinasco and he jumped out of the gate in the final round on Sunday with a birdie at the par-5 first.
The Englishman found trouble with a bogey at the par-4 third, however, and his shaky front nine continued with a bogey at the par-3 eighth. Webster responded with a birdie at the following hole and played his approach to 12 feet for a birdie at the par-4 10th.
With several players applying pressure to the top of the leaderboard, Webster drained a 10-foot putt for a birdie at the par-4 13th to remain in first. Webster then began to pull away with a birdie at the par-5 15th after he reached the green in two.
At the par-4 17th, Webster dropped his second shot inside 10 feet and ran home the birdie putt to move to 18-under. Webster then parred the closing hole to win by three strokes.
'I was concentrating really hard,' said Webster. 'My mind was racing ahead. I always thought I could win and with nine holes to go I was telling myself you are going to win this. But to make the winning putt with a couple of shots in hand was a great feeling.'
Hansen tallied a pair of birdies and a bogey over his first four holes. He added back-to-back birdies starting at the par-5 ninth and picked up a birdie at the 12th to move to 13-under.
The Dane continued his fine play with two straight birdies from the 14th, but he looked to be in trouble at the par-3 16th after his tee shot found a greenside bunker. Hansen hit out to 12 feet and rolled in the putt to save par. He managed a couple of pars on his closing holes to finish in a tie for second.
Finch, the 36-hole leader, stumbled to a bogey at the par-4 second and hit his tee shot in the water en route to a double bogey at the par-3 eighth. The Englishman persisted and collected three birdies over his next four holes to get back to minus-13.
Finch sank a 10-foot putt for a birdie at the 15th and drained a 20-footer for a birdie at the 17th on his way to a round of 70.
Dredge picked up a birdie at the first and another at the fourth to grab a share of the lead. He struggled to a bogey at the very next hole, however, and faltered again with a bogey at the 10th.
The Welshman hit his second shot to 6 feet for a birdie at the par-4 11th and made it two in a row with a birdie at the 12th. Dredge then birdied the 14th and the 17th to get to 16-under, but a bogey at the last left him three shots off the pace.
Simon Khan suffered a quadruple bogey at the 18th to fall back into a tie for sixth place with Gonzalo Fernandez-Castano, Jamie Spence and Andrew McLardy at 10-under-par 278. Gary Orr, Marcel Siem, Stuart Little and Adam Groom followed at 9-under-par 279.