Robert Rock carded a breathtaking, record breaking 60 at Lahinch Golf Club to take a one shot lead into the final round of the Dubai Duty Free Irish Open.
The Englishman's ten under par effort is the lowest round in the history of the event and matches Brandon Stone's record for the lowest round in the Rolex Series.
It also bettered Rock's best ever European Tour round by three shots and handed him a 13 under par total, one clear of Spaniard Rafa Cabrera Bello and England's Eddie Pepperell.
South African Zander Lombard was at 11 under, with England's Andy Sullivan and Austrian Bernd Wiesberger three shots off the lead.
Rock birdied his final six holes and had a 35 foot putt for eagle on the last but missed by inches on the low side to be denied just the second 59 in European Tour history.
And in a remarkable twist of fate, Rock's caddie Gary Tilston is the twin brother of Guy Tilston, Oliver Fisher's caddie when he recorded the history making first 59 at last season's Portugal Masters.
Rock famously took home the winner's cheque at this event in 2009 despite losing a play-off to Shane Lowry as the home favourite was still an amateur, and he could be claiming a third European Tour title as well as the 1,166,660 euro prize on Sunday.
"That's the first chance I've had to do it," he said of his potential 59. "It's disappointing not to but 60 is a great score. It's my best score.
"I played rubbish so far this year, so just delighted to play better. It is a good opportunity, it's an opportunity to get my season back on track, to try to qualify for The Open and maybe have a chance to win a tournament again, which would be lovely because it's been a long while.
"Any time you've got a chance to win a tournament like the Irish Open or Scottish Open, it really means something, it gives me a little extra focus.
"It's hard to say it makes you play great because you can't force that but it's a great tournament and the people are amazing. I think the quality of the golf course is just fun to play."
Rock turned in 31 with birdies on the first, third, sixth and ninth and a bogey on the fourth, but when he made another gain on the tenth he was still two off the lead.
His incredible birdie run started on the driveable 13th and an approach to 13 feet on the next had him in a share of top spot.
He put an approach to eight feet on the 15th and holed a 20 footer on the next but the best was yet to come as he rolled home from 65 feet on the 17th.
The 42-year-old admitted he did not know that 59 was on until before his second shot at the last but he did not seem fazed, finding the fringe and being a whisker from history with his putt.
Cabrera Bello already has one Rolex Series title to his name and much like Rock he truly came to life on the back nine in his 63.
The 2016 Ryder Cup star birdied the fourth, fifth, seventh, ninth, tenth and 12th but bogeys on the second and sixth meant Rock's clubhouse lead remained at four shots.
An up-and-down on the 13th trimmed it and Cabrera Bello then put his tee shot at the par three 16th to 12 feet before getting up and down again on the last for a closing birdie.
Pepperell parred his first 12 holes before holing from ten feet on the 12th and three feet on the 14th.
Bunker trouble led to a bogey on the next but he hit a stunning tee shot on the 16th, put an approach to three feet on the next and took advantage of the par five last in a birdie-birdie-birdie finish.
Overnight leader Lombard was three over for his round after eight holes but hit back with birdies on the ninth, tenth, 13th, 16th and 17th.
Wiesberger took 65 shots, one fewer than Sullivan, while Frenchman Mike Lorenzo-Vera and Northern Ireland's Cormac Sharvin both carded rounds of 66 to sit at nine under.
World Number 11 Jon Rahm, fellow Spaniard Jorge Campillo, Scot Grant Forrest and English duo Paul Waring and Oliver Wilson were five shots off the lead.
