By Rory Carroll

Clark sank a short par putt on 18 to finish the championship on 10-under par 270 behind an impressive display of power and precision.

“I’ve worked so hard and dreamed about this moment for so long,” said Clark while collecting the trophy and winner’s check of $3.6 million.

“So many times I’ve visualized being in front of you guys and winning this championship. I felt like it was my time.”

World number one Scottie Scheffler was third at seven under while overnight co-leader Rickie Fowler faded early and had to settle for a share of fifth.

Clark overcame trouble around the turn and looked to be in total control when a birdie on 14 pushed his lead to three shots with four holes to play.

He ran into trouble with a bogey on the short par-three 15th and his advantage shrank to a single stroke when his par putt lipped out on 16.

But he held his nerve to make par on the two long closing two holes, while McIlroy failed to sink a 41-foot birdie putt on 18 that would have moved him into a tie for first.

“It’s tough on the back nine trying to win a tournament but I felt at ease,” Clark said.

“I just kept saying, I can do this, I can do this.”

He said he drew inspiration from his late mother.

“I felt like my mom was watching over me today,” said Clark, who considered quitting golf a decade ago after his mother died of breast cancer.

(Reporting by Rory Carroll in Los Angeles;Editing by Peter Rutherford)