Despite the best efforts of Christiaan Bezuidenhout, Billy Horschel and Patrick Reed, the final 18 holes developed into a two-horse race between the final pair, and it was the unflappable Willett who came out on top to land his seventh European Tour title, and his first since winning the final event of last season in Dubai.
After starting the round locked together at 15 under after Rahm’s faltering finish on Saturday, Willett struck an early blow when he drained a 25-foot putt for birdie on the second hole, and he doubled his advantage from half that range on the next green.
Rahm appeared to be a little out of sync with his irons, but he did find the green in two at the long fourth and shaved the hole with his eagle putt, settling for a birdie which Willett could not match after he bunkered his approach.
But after trading pars over the next three holes, Willett regained his two-shot lead with another perfect putt at the eighth, and he did well to scramble a par after a poor drive at the ninth to maintain his advantage as Rahm carded his eighth par of the front nine.
Rahm then got a big putt to drop for birdie at the 10th and Willett followed him in from six feet, and the former Masters champion again displayed his scrambling qualities at 11 when his wayward drive bounded into the pines, one of which he hit with his attempted recovery shot.
Willett hacked his third from the heather into a bunker and knocked his fourth onto the front of the green, and he was celebrating a bogey moments later when his 35-foot putt for bogey had just enough pace to drop as Rahm settled for another par.
Perhaps rattled by Willett’s escapology, Rahm then drove into a fairway bunker at the 12th and, after coming up short with a pitch, he ran up an ugly bogey-six on a hole he had birdied the previous two days, although he remained only two behind when Willett was unable to make his fourth birdie of the week on the par-five.
But Rahm did make it three birdies for the tournament at the 13th, only to give the shot straight back when he was a club short with his tee shot to the 14th and could not get up-and-down from the sand, with Willett enjoying a solid par to restore his two-shot lead with four to play.
2:22 Danny Willett reflects on his resurgence after victory at the BMW PGA Championship at Wentworth.
Rahm was about to celebrate a 20-foot birdie putt on the 15th green, only for his ball to roll around the lip and stay out, and both parred 16 to leave Willett two up with the two par-fives to contend with.
Willett guaranteed himself another birdie at 17 with a sublime pitch to 18 inches, but Rahm kept his fading hopes alive with a birdie of his own from six feet but, realistically needing an eagle at the last to force a play-off, the Spaniard’s drive drifted a little too far left, costing him at least 20 yards in distance.
Rahm’s ambitious second failed to make the carry over the stream short and right of the green, although his mistake mattered little in the outcome as Willett nailed his drive and drilled a superb second to the heart of the green, from where he calmly two-putted for his sixth birdie of the day.
To his credit, Rahm got up-and-down from the drop zone to save par and hang on to outright second in an impressive debut at the West Course – his seventh top-10 finish in his last nine tournaments worldwide.
Bezuidenhout briefly shared second with Rahm when he birdied 16 and 17 to move to 16 under, although he could only par the last for a 68 which ensured outright third ahead of star American duo Horschel and Reed, with Horschel matching his Friday 65 while Reed carded an eagle and four birdies in a bogey-free 66.