The Open: Rory McIlroy and Viktor Hovland share lead at St Andrews after third round

Rory McIlroy and Viktor Hovland take a four-shot lead into the final round of the 150th Open Championship after a scintillating duel over the Old Course.

The Ryder Cup team-mates delighted the St Andrews crowd as they both shot six-under-par 66s to lead on 16 under.

McIlroy, who is trying to end an eight-year major drought, holed a bunker shot for an eagle two on the par-four 10th but had his solitary bogey on the 17th.

Cameron Smith and Cameron Young are tied for third on 12 under par.

Overnight leader Smith, who led by two at the start of play after a nerveless putting display on Friday, spluttered on the first, missing a three-footer for par, and that set the tone for the Australian, who carded a 73 and was one of only two players in the top 20 to shoot over par.

A run of seven pars followed his bogey at the first, dropping him down the leaderboard as those around him made birdies and eagles in the most benign conditions of the week.

Hovland, who is yet to win one of golf's biggest prizes, struck the early blows with a run of four birdies from the third to get to 14 under but McIlroy - a four-time major winner - hit back with three of his own by the ninth.

That drew the Northern Irishman level with Smith and put him one behind Hovland.

But a sensational 10th hole saw the world number two, who won this title in 2014, hit the top of the leaderboard.

McIlroy visited the sand for the first time this week, with an errant tee shot. He backed off his ball a couple of times before settling and striking the perfect blow, his ball landing a dozen feet short of the pin and rolling in. The cheers that greeted it startled world number one Scottie Scheffler who was about to tee off on the adjacent par-three 11th.

"The eagle was a bonus but I was pretty proud that I kept my composure over the next few holes, not to drop a shot or get ahead of myself and I played well down the stretch," the 33-year-old told BBC Radio 5 Live.

As the eagle dropped, Hovland smiled, as Hovland does. The 24-year-old world number nine composed himself and got down in two from the front of the green for a birdie. The pair locked on 15 under.

They would stay that way for three holes, breaking the tension with a laugh and a joke while waiting on the 12th tee. McIlroy said at the start of the week "boring golf" was needed to win a major. Par. Par. Par.

To the 14th. The longest hole on the course. Hovland just short in two. McIlroy turned the screw, hammering an iron into the heart of the green. A two-putt birdie heaped pressure on the Norwegian. Three putts. Par. The roars growing louder as they headed back towards town.

"I certainly appreciate the support," said McIlroy. "I feel it out there but I just have to stay in my own little world. I've done it well for three days so I just have to do it for one more day."

Meanwhile, Smith was melting on the 13th. With his feet in a bunker and the ball at waist height, he tried the kind of shot only Seve Ballesteros could play. A wild swipe careered into more trouble. The world number six tried again to advance his ball to the green. It went left and a double-bogey six was marked on the card as he tumbled to 11 under.

From three behind, McIlroy was now five ahead of Smith, who knows how to win on the big stage, having claimed the PGA Tour's flagship Players Championship in March.

Smith's playing partner Cameron Young played steadily, the American picking up birdies at the two par-five holes and the short par-four ninth and 10th holes to keep the leaders in sight at 14 under after 14. But a horrible chip through the green on the 16th led to a double bogey.

Up ahead, McIlroy and Hovland followed each other over the back of the green on the treacherous par-four 17th.

McIlroy's chip from near the wall crept on to the green but the 24-foot par putt sidled six inches wide.

Hovland chose to putt from a gravel path and knocked his ball to four feet and holed for par, his eighth in succession.

"That was a lot of fun. To shoot bogey free at a major in these conditions was pretty special," Hovland told the BBC.

They were locked again at 15 under, McIlroy's mantra of "boring golf" wins majors ringing true.

And that became 16 under three blows later on the 18th - a hole that ranked as the easiest on the course, almost guaranteeing a birdie.

Except for Smith and Young, whose rounds fizzled out with scruffy pars.

Others briefly challenged but then faltered in the closing holes. Scheffler improved from eight under to 12 under with a birdie on the 11th, while Dustin Johnson also reached that mark on the 10th.

Scheffler gave his shot back at the 12th though and dropped another on the 17th before finishing with a birdie and an 11-under total after a three-under 69 - the same score as South Korea's Kim Si-woo, who had a 67.

That was one better than Johnson, who had three bogeys on the back nine as he signed for a 71.

The English challenge sits seven back. Tommy Fleetwood had the better day with a 66 to get to nine under, while US Open champion Matt Fitzpatrick's 69 lifted him to the same total.