But the last six holes of Johnson’s round were played with the threat of a penalty hanging over him.

The American’s ball had moved as he prepared to putt on the fifth hole. He conferred with the referee at the time and he, the referee and playing partner Lee Westwood all agreed he had not addressed the ball and could take his shot as usual.

But on the twelfth hole he was told the USGA wanted him to review footage of the incident after the round, with the possibility of a one-shot penalty for touching the ball.

All the other golfers were also made aware of the situation and so the final hours of the competition were played out with uncertainty over the score of one of the leaders.

Rory McIlroy led a chorus of protest from golfers - who were all firmly behind Johnson and appalled at the decision to leave the penalty undecided until afterwards.

This is ridiculous... No penalty whatsoever for DJ. Let the guy play without this crap in his head. Amateur hour from @USGA

— Rory McIlroy (@McIlroyRory) June 19, 2016

Lemme get this straight.. DJ doesn't address it. It's ruled that he didn't cause it to move. Now you tell him he may have? Now? This a joke?

— Jordan Spieth (@JordanSpieth) June 19, 2016

No way DJ gets a penalty. Use some common sense @usga The greens are running 14 and are sloppier than Mount Everest

— Luke Donald (@LukeDonald) June 19, 2016

Johnson showed great resolve to close out his round in impressive style despite the controversy and finished with a score of four under after the one shot penalty.

USGA officials were interviewed afterwards and explained the logic behind their ruling.

“When you look at the video and the proximity of the putter near the ball and the ball moving shortly after, we felt we had a situation we ought to alert Dustin to."

They then went to speak to the golfer: “Dustin, what we saw on the video was a concern.”

USGA officials explain their decision to give Dustin Johnson a one-stroke penalty. #USOpenhttps://t.co/pMeHKBLx9a

— FOX Sports (@FOXSports) June 20, 2016

But the explanation hasn't satisfied golf fans unhappy with the messy tournament end - regardless of Johnson’s eventual win.

DJ took the high road to take that penalty. This ordeal cannot be overlooked because of a multiple shot victory

— Jordan Spieth (@JordanSpieth) June 20, 2016

Clarity of the score at any given time is the very essence of competitive sport - this must not happen again @SkySportsGolf @usopengolf

— Paul McGinley (@mcginleygolf) June 20, 2016

I can't find one person supporting the USGA and there in lies the problem

— Hank Haney (@HankHaney) June 20, 2016

Looks like the @USGA can't/don't follow their own rules! Make it up as they go along! #Farcical #STP pic.twitter.com/e8sqEhm1fB

— Secret Tour Pro (@secrettourpro) June 20, 2016