By Mark Garrod, PA Sport Golf Correspondent, Chicago

Londoner Brian Davis came back down to earth with a bang today after producing the fastest start in United States Open history.

Davis, making his debut in an American major, pitched in from 72 yards for eagle on the first hole, then birdied the next three to stand five under par and outright leader.

"I'll wake up in a minute," he told his caddie. And he did.

A double bogey came on the very next hole and in the end he finished with a one-over-par 71 to be six behind playing partner Brett Quigley.

"I was in shock," stated Davis, who qualified last week and then flew home both to play in the British Masters and spent time with his wife Julie, who has now been taken into hospital for tests after collapsing.

He also had the setback on arrival at Olympia Fields of having his two-iron stolen from the locker room.

"It was a club I needed and the replacement's not the same," he said. "The adrenalin was really flowing, but the main difference playing in an event like this is mentally. It really gets you and I lost my momentum."