World Golf Championships: Dustin Johnson holds off Tommy Fleetwood to win in Mexico

Johnson joins Tiger Woods as the only players to have won at least four WGC titles

American Dustin Johnson held off a strong European challenge to win his first tournament as world number one at the World Golf Championships in Mexico.

Johnson, 32, closed with a round of 68 to finish 14 under par, one shot clear of England's Tommy Fleetwood (66).

Another Englishman, Ross Fisher (65), was tied for third on 12 under with Spanish rookie Jon Rahm (68).

Northern Ireland's Rory McIlroy, the halfway leader, did not threaten as he ended with a level-par 71 for 10 under.

Johnson moved to the top of the rankings last month and becomes only the fifth player after Ian Woosnam, David Duval, Vijay Singh and Adam Scott to win his first tournament after becoming number one.

"It means a lot - it's a tough spot to be in," said Johnson. "There a lot of pressure on you. I played just well enough I guess, because I won by one."

Johnson looked to be cruising to victory when he led by four shots midway through the final round but he was briefly overhauled by Rahm.

The 22-year-old from northern Spain is based in the US but confirmed last week he had taken out affiliate membership of the European Tour to be eligible for the Ryder Cup team.

A victory in his maiden WGC event looked possible when Rahm moved to 14 under - and a one-shot lead - with birdies on 14 and 15, but successive bogeys followed to leave him in a tie for third.

Fleetwood closed with two rounds of 66 to finish second

Southport's Fleetwood, 26, sank a superb 40ft putt on the last to secure second place on his own, and with it a cheque for £850,000.

Fisher, from Ascot, surged into contention with nine bogeys in a final round that left the 36-year-old tied with Rahm in third place.

"That last putt [a birdie at the 18th hole] was a big one wasn't it?" Fleetwood said. "It was just nice to have a chance going down the stretch and it just shows you're never quite out of it if you just hang in there."

Frustrating afternoon for McIlroy

Two strokes from the lead starting the day, McIlroy missed a seven-foot birdie chance at the first hole, which set the tone for a frustrating afternoon.

"I needed to get off to a fast start and I didn't. The course got a little tricky over the weekend and maybe I didn't adjust to that," said McIlroy, who had returned to action following a seven-week lay-off with a rib injury.

"First start back, it's OK, but being two ahead going into the weekend [it is] obviously disappointing to finish where I have.

"These two rounds were the sort of rounds I would have expected the first two days, not the last two. I was hoping to improve as the week went on."