Conor O’Rourke came through what club aficionados believe was the longest match in the history of the South of Ireland Championship — 27 holes — before beating leading qualifier Rowan Lester with a birdie at the 18th to reach the semi-finals after a stunning day's golf at windy Lahinch.

The 25-year old Walker Cup prospect from Naas had to go nine extra holes to beat Laytown and Bettystown’s Thomas Mulligan in the third round before coming back from one down with two to play to beat Lester by one hole thanks to a par-birdie finish in the Pierse Motors Volkswagen sponsored classic.

“Thomas made a great birdie from 12 feet on the 18th to take the match up the 19th and I was just happy to get through on the 27th,” O’Rourke said of the marathon third round win that was followed by an equally enthralling win over Lester.

“The match this morning was brilliant but the match this afternoon was probably better. Rowan is a very good player and he has come on an awful lot. I was just glad to get through it."

Mulligan, who will play in the NI Open on the Challenge Tour before heading to the University of Oregon at the end of August, was sensational throughout but left to rue several putts that stopped on the lip and one that went too far.

After leaving birdie putts just short at the sixth and seventh tie holes, he holed an eight footer for birdie at the eighth to force O'Rourke to follow him in from four feet but lost at the ninth extra hole when he knocked a 20-foot birdie chance nearly four feet past and missed the return.

O'Rourke dodged a bullet there but he showed remarkable resilience throughout the day, especially against Lester in what was a sensational clash that went right to the final green

"I was one up, then he won two in a row to go one up and I won two in a row to go one up," O'Rourke said.

"Then he made an unbelievable birdie on 14 from 230 yards from the long stuff to go back one up. I won 15 to level, he won 16 to go one up."

At the end of a gruelling week of high winds and slanting rains, the match was decided on minor details.

Lester's poor drive at the 17th led to a bogey that left them all square heading to the par five 18th.

The Hermitage man was 20 yards behind O'Rourke in the middle of the fairway but despite hitting a decent approach, he left himself a tricky pitch from an upslope near the greenside bunkers on the right and was unlucky to see it kick forward off a downslope and run 12 feet past.

O'Rourke was just off the left edge in two and chipped dead to secure his birdie before Lester, the reigning North of Ireland champion, failed to find the line or pace with his putt to stay alive and bowed out.

"It was tricky out there," O'Rourke said. "But I was just very, very patient. They are all tough games and while I have played well in all my matches, there has been nothing in them. 

"They have all been close. So it's been a gruelling week but I am fit and ready to give it a rip tomorrow and see what happens." 

O’Rourke now faces and former college team mate Barry Anderson from Royal Dublin, the reigning West of Ireland champion, in this morning’s semi-finals after the Rosses Point born accountant chiselled out a pair of one-hole wins over Rosslare’s Paul Murphy and Clandeboye’s William Russell.

Anderson was one down to Russell with three to play but birdied the 18th from 12 feet, getting up and down brilliantly from a greenside bunker for the win to remain in with a chance of becoming the first player to win the "West" and the "South" in the same season since JB Carr in 1948.

The winner of the O’Rourke-Anderson clash will meet the winner of the all-Cork showdown between Irish Amateur Open champion Peter O’Keeffe from Douglas and 20-year old Mallow talent James Sugrue. 

And it looks set to be an all action affair with both Munster men clearly opting for attack.

A former Challenge Tour professional, 35-year old O’Keeffe beat Kinsale’s Cathal Butler 2 and 1 in the morning before closing out 2009 champion Robbie Cannon from Balbriggan 3 and 1 in the afternoon by holding up a stunning, 183-yard six-iron into the stiff westerly breeze, leaving himself a three footer that was eventually conceded.

Should O'Keeffe add the "South" to his Irish Strokeplay victory at Royal County Down last May, he would surely earn a call up for the Irish team that will be bidding for a fourth successive win in the Home Internationals at Moortown next month.

But the big Corkman is simply focussed on winning another amateur major, and unlike his surgical approach to the Royal County Down, where he hit irons most of the week, his aggressive tactics at Lahinch have paid off so far.

"I will be hitting driver everywhere, as I have done all week," said O'Keeffe, who can become the first man to win the Irish Amateur Open and South of Ireland titles in the same year since the great Lionel Munn in 1911

 "I have had little or no success here in the past, so I decided I was going to take it on. 

"I have been taking very aggressive lines and being accepting of where the ball goes."

Sugrue does not have any fairway woods in his bag bar the driver, and an interesting tussle seems assured as he announced, "I will be going for it against big Pete."

The former Boys international — a former winner of the Connacht Boys and Munster Youths titles — beat Cork’s Gary O’Flaherty 4 and 2 before coming back from three down after nine holes to beat Kinsale’s John Murphy 2 and 1.

"I was expecting to do well this week," said Sugrue. "I don't live far away, and I know the course very well. But I am obviously delighted to get through. 

"I was playing nicely in the North and qualified well. Then I missed my tee time for the first match, so I said I have to redeem myself after that, so I did a lot of practice during the week."

Mallow Golf Club already has plans to present Sugrue with an alarm clock, whatever the result on Sunday. And he looks like a tough opponent for O'Keeffe after he showed great patience against Murphy, who came from behind to beat international Colm Campbell from Warrenpoint on the 19th.

"Three down after nine, my caddie just said I had to take it as little three-hole matches and win the first one, then win the second one," Sugrue said. 

"As it turned out, I won 10, 11 and 12 with pars to get back to all square."

With Murphy out of kilter with his swing, Sugrue won the 14th and 16th in pars to go two up before closing out the match at the 17th.

"I am looking forward to it," he said of Sunday's semi-finals. "If there was any championship I could win, it would definitely be the South. 

"It's definitely the most fun and it's the oldest one. And Lahinch is a class spot!"

O'Rourke remains the clear favourite after remaining cool and collected throughout a 45-hole day.

Including strokeplay qualifying, last year's St Andrews Links Trophy winner has had to play 109 holes to reach the last four compared to 101 for Anderson, 106 for O'Keeffe and 104 for Sugrue.

116th South of Ireland Amateur Open, sponsored by Pierse Motors Volkswagen

Round three - Saturday, July 29

1. Conor O’Rourke (Naas) bt Thomas Mulligan (Laytown & Bettystown) 27th;
2. Rowan Lester (Hermitage) bt Pat Murray (Clontarf) 2/1;
3. Barry Anderson (The Royal Dublin) bt Paul Murphy (Rosslare) 1 hole;
4. William Russell (Clandeboye) bt Rory Williamson (Holywood) 1 hole;
5. Robbie Cannon (Balbriggan) bt Jake Whelan (Newlands) 3/2;
6. Peter O’Keeffe (Douglas) bt Cathal Butler (Kinsale) 2/1;
7. John Murphy (Kinsale) bt Colm Campbell Jnr (Warrenpoint) 19th;
8. James Sugrue (Mallow) bt Gary O’Flaherty (Cork) 4/2.

Quarter-finals - Saturday, July 29

1. Conor O’Rourke (Naas) bt Rowan Lester (Hermitage) 1 hole;
2. Barry Anderson (The Royal Dublin) bt William Russell (Clandeboye) 1 hole;
3. Peter O’Keeffe (Douglas) bt Robbie Cannon (Balbriggan) 3/1
4. James Sugrue (Mallow) bt John Murphy (Kinsale) 2/1.

Semi-finals - Sunday, July 30

1. (08:30) Conor O’Rourke (Naas) v Barry Anderson (The Royal Dublin)
2. (08:45) Peter O’Keeffe (Douglas) v James Sugrue (Mallow).

Final - 2 pm