By Norman Dabell
McDowell's fifth European Tour victory came with a blistering final round eight-under-par 63 at Celtic Manor for a four-round 15-under 269 aggregate, three strokes better than fellow Briton Rhys Davies.
As he did last week in Madrid, Northern Irishman McDowell, 30, came flying out of the blocks, claiming six birdies in the first eight holes to storm past struggling overnight leader Marcel Siem of Germany.
Siem, leading the field by three strokes after round three and McDowell by four, lost the tournament as early as the short third. Here he dumped two balls in the lake to run up a quadruple-bogey seven to plummet down the field.
Last week's runner-up Davies became McDowell's only realistic hurdle as the Welshman delighted the home gallery with a sizzling round of his own. The 25-year-old carded a 62 to better the Twenty Ten course record by a stroke.
Davies, second to Luke Donald in the Madrid Masters, mounted his challenge largely by virtue of two eagle-twos. At the eighth he holed out from 160 yards with his eight-iron second shot and when he ran in a 30ft putt on the reachable par-four 15th he was only a stroke behind McDowell.
McDowell responded with birdies on 10 and 11 as he refused to loosen his grip on the 350,940 points on offer for first prize which took him to 10th on Europe's Ryder Cup table.
(Editing by Justin Palmer)