Playing on the course where he hopes to earn his second cap against the Americans in October – quite possibly as Rory McIlroy’s partner – the 30-year-old was forced to pull out all the stops to grab his fifth European Tour title.
In-form Welshman Rhys Davies was the man to put the heat on with a stunning course record 62 that saw him cover the middle 12 holes in 10 under par.
But McDowell matched the 25-year-old’s front nine 30, started for home with two more birdies and, with a three-stroke lead once Davies had bogeyed the difficult 16th, did not let the opportunity slip.
A closing 63 for a 15 under par total of 269 gave McDowell, winless since the 2008 Scottish Open, the £300,000 first prize by three and left Davies a runner-up for the second week running.
McDowell’s 64-63 finish – he feared he was going to miss the cut on Friday – was only three outside the best ever on the circuit.
“I think it’s the best final round I’ve ever played to win a tournament,” he said.
“The first 11 holes was dream golf and I am ecstatic. I feel I’m in the form of my life right now and I really feel that I have a big event in me.”
The size of the cheque was still not enough to put McDowell into an automatic qualifying place in the points race, but the odds on him receiving a wild card if need be should come crashing down because of where this was.
“To win around here is certainly going to stand me in good stead if I need a pick,” he added.
Four behind at the start of the day McDowell could not have expected to become the man to catch so quickly, but overnight leader Marcel Siem of Germany put two balls in the water and ran up a quadruple bogey seven at the short third.
Davies, eight adrift when he teed off, knew he was in with a chance from the moment he sank his 170-yard eight-iron for an eagle two on the eighth.
His fourth birdie came on the next, then he produced two more at the start of the inward half and when he drove the green at the 377-yard dogleg 15th and made his 30-foot putt for another eagle two the European Tour’s first-ever 59 was still a possibility.
The Tour rookie required two more birdies for that, but instead he failed to get up and down from sand on the next and had to settle for two closing pars.
His round nevertheless shaved a stroke off the course record set by Scotland’s Stephen Gallacher in the third round and matched by his fellow Scot Marc Warren early on the final day.
Davies stated: “I enjoyed every second. I went out very relaxed – I tried to push too hard yesterday and was mindful of that.”
He admitted he thought of 59 at one point, but “put it aside very quickly”.
He added: “I tracked what Graeme was doing. He continued to make birdies, so I kept my head down and tried to make some more. I tried my best, but it didn’t quite happen for me.”
Third place went to Luke Donald, the man who pipped Davies in last week’s Madrid Masters. His three-week trip back to Europe has brought him a win, a second and a third and the Englishman is even closer now to regaining his Ryder Cup spot.
Gallacher shared fourth with England’s Robert Rock and Italian Edoardo Molinari, but Siem fell back to seventh with a 74.
Damien McGrane and Peter Lawrie were second best of the Irish, both players closing with 71’s for a total of 282.