Luke Donald beat Lee Westwood in a play-off to win the PGA Championship at Wentworth and overtake his countryman as the world number one.
The 33-year-old Donald won at the first play-off hole when Westwood found the water in front of the 18th green.
Donald hit 70 to Westwood's 68 to tie on six under, while Englishman Simon Dyson (69) was third at four under.
On climbing one spot to the top of the rankings, England's Donald said: "Sounds pretty good, doesn't it?"
The American-based golfer added: "It's something I'll be very proud of. Obviously, there's a lot of work still to do and hopefully there'll be much more to come, but I'll savour this.
"It's a lot of responsibility and I'm looking forward to the challenge of being number one and hopefully I can hold onto it for a few more weeks. I know Lee and Martin [Kaymer] will be chasing me hard.
"To come through in these circumstances in one of the biggest tournaments in the world, going head-to-head with Lee is pretty special. It doesn't get much better.
"To win here with the top three in the world, top six out of seven, all of the Ryder Cuppers, all four major champions, and to beat them in stroke play feels pretty good."
The second-ranked Donald, who has been vying for top spot for a number of weeks, only needed to finish above Westwood to take the reins, as long as world number three Martin Kaymer finished outside the top two.
But with Kaymer struggling down the field, the final day was set up for a duel between the world's two best-rated players.
Donald, who was second at Wentworth last year and won the WGC Match Play in February, began tied for the lead with 18-year-old Italian Matteo Manassero, with Westwood two back in the penultimate group.
But Donald, who fought back from a messy outward 40 with an inward 32 on Saturday to bring back memories of his first-round 64, was soon in trouble again. His opening drive went deep into the trees on the right and he could only hack out sideways, eventually running up a bogey, followed by another at the short second after a poor chip.
Manassero's challenge was effectively over after a double bogey on the third and Westwood joined Donald in a share of the lead with a birdie at the fourth.
From then on the lead was virtually a two-horse race. Westwood finally went clear on his own with a birdie on the 12th to reach six under and he forged a two-shot cushion with another birdie on 15. But the 38-year-old handed a shot straight back on the 16th when he raced his first putt 10ft past and missed the one coming back.
Donald, who had recovered with birdies at the fourth and 10th, hit his approach on 16 to a few inches and tapped in for another birdie to draw level again. Both players escaped with par fives on the 17th, and although Donald recovered to make par after driving into a fairway bunker, Westwood missed a birdie chance that would have proved decisive.
"I played lovely all day," said Westwood. "The reason I finished second was because I didn't take my chances on 17 and 18, not because I lost the play-off."
Playing the long 18th again, Donald's third shot to the green span back to about 10ft from the pin, while Westwood's effort screwed into the water guarding the front of the green, the controversial change to the famous finishing hole which was instigated in 2010. The Worksop star chipped on but could only make seven and Donald holed his putt first time for the title - his fifth of the year to continue a remarkable run that has seen him finish in the top 10 in his last nine events.
Of the man he beat, Donald added: "I felt a bit bad for Lee. I knew it would be a tough play-off. Lee's a hell of a player and doesn't back down."
Ireland's Shane Lowry finished birdie, birdie, eagle to shoot 67 and finish tied for fourth at two under alongside Australian Marcus Fraser (67) and Frenchman Raphael Jacquelin (71).
Three-time PGA champion and eight-time European number one Colin Montgomerie carded 68 to end in the group sharing seventh at one under for his best finish since a tie for second in the 2008 French Open.
Manassero, already a two-time winner on Tour after turning pro in 2010, ended with a 75 to also finish one under alongside England's David Horsey (71), Wales' Jamie Donaldson (69), Scot Peter Whiteford (70) and Sweden's Johan Edfors (71).