He will start the final round at nine under, alongside countrymen Xander Schauffele (67) and Kevin Kisner (68). Another American, Kevin Chappell (67) is a short further back in outright fourth place.

If Spieth prevails on Sunday afternoon, he will have claimed his fourth major title before the age of 25. Tiger Woods was 24 when he won his fourth, while Jack Nicklaus and Rory McIlroy were both 25.

Everything went to plan for Spieth right from the start on day three. He attacked the par-4 opening hole with a driver, which saw his ball bound down the baked fairway and trickle onto the front edge of the putting surface about 15 feet from the cup. When he rolled the putt in for an eagle two he was just a shot out of the lead.

Jordan Spieth salutes the crowd after holing his putt for eagle at the 1st hole. PHOTO: Getty Images.

Spieth, who is aiming to win his fourth major championship, didn’t take a backward step all afternoon. He missed just three greens in regulation and, when he did miss, he was nerveless in draining his par-saving putts.

“Today's round was about playing No. 1 the way I need to play No. 1, take it shot by shot, hit it into the spots, miss it in the right spots,” Spieth said.

“He went a little high and tight ... It was intended to be what I normally get, and instead he went a little shorter. A very British haircut." – Jordan Spieth.

“I got a couple of good breaks. The drive on 10 was a little wayward. Ended up to where I could hit the green. I got up and down on 12, and then my tee shot on 14, that par-5 missing the bunker by a couple yards and having a good enough lie to reach the green. So I got a couple good breaks.”

The 24-year-old is looking to make the first successful Open defence since Padraig Harrington in 2008. Last year, he took a three-shot lead into the final round but he says sharing the lead will actually make him sleep easier tonight.

FULL OPEN LEADERBOARD

“I think I’ll sleep easier for sure,” he said. “And the fact that I won last year, I think helps sleep a little bit.

“I don't find any expectations right now. I feel pretty calm because of the progress made in the game. If I felt like I got away with a lot of stuff and I really wasn't progressing and just made a lot of putts, then I'd probably feel more tension.

“But I like where the (ball) striking's at. It can improve a little bit, but all aspect of the game got better today.”

Spieth said his victory last year was about proving himself to the golf world, but he’s now playing for himself and realises, on a predicted windy day, the challengers will come.

“I had something I had to prove to other people with last year's Open and to myself,” he said. “I don't feel like I have to prove anything to anyone at this point. I'm playing golf for me now.

Whenever Spieth got in trouble, he found a way to get his ball into the hole without losing any shots to the field. PHOTO: Getty Images.

“I've got an opportunity to make it a very memorable one with a round, but it's not necessary for me to prove anything for any reason. I feel like my game's in good shape.

“It's ideal for Carnoustie to have a bunched leaderboard and 25-mile-an-hour winds on Sunday because it means that someone could post a score from six hours before and potentially win the golf tournament tomorrow. So I'm not ahead of myself at all.”

Perhaps the only thing that didn’t go to plan for Spieth on day three was a morning haircut at a barber on the Carnoustie High Street.

“He went a little high and tight,” Spieth laughed. “It was intended to be what I normally get, and instead he went a little shorter. A very British haircut. A little shaved on the sides, a little longer on top. It is what it is. Summertime, it works out.”

The young Texan said he didn’t think the barber recognised him and “he didn’t really say much” during the £9 trim but “I tipped him” anyway.