Mikko Ilonen carded a course record 64 at Fota Island Resort to establish a two shot lead after the first round of the Irish Open.
The 35 year old from Finland made eight birdies and dropped just the one shot during his seven under par effort, which left him two clear of Germany’s Marcel Siem, former European Number One Robert Karlsson and his fellow Swede Magnus A Carlsson.
Having turned in a three under 32 Ilonen bogeyed the first – his tenth – after missing the green with a wedge in hand.
Ilonen, who won the British Amateur title in 2000 at next month's Open Championship venue Hoylake, is looking to climb into the Official World Golf Ranking's top 50 for the first time and boosted his chances with five birdies in his last seven holes.
“It was a slow start really,” said Ilonen, who lost a play-off to Sergio Garcia for the Commercial Bank Qatar Masters earlier in the year.
“The first sort of four or five holes I felt like I can't get anything going, but I stayed patient and then the birdies kept coming. In the end I managed to hit a couple of good putts which was nice.”
Siem stormed home in just 29 shots – almost holing his approach to the 14th in the process – as he carded seven birdies and two bogeys in his round of 66.
That was swiftly matched by Karlsson, who would have held second outright but for a missed five footer at the last following a sensational wedge approach.
The 44 year old has gone four years without a European Tour victory, but showed signs of return to form with a brilliant closing 63 at the recent Nordea Masters and started here with a bogey-free round.
"It was nice, I'm very, very happy," said Karlsson.
"I worked quite hard when I've been at home since the Nordea Masters, so it's been nice to keep it going.
"I've done a bit of work with my coach and things are coming together quite nicely. The long game was very, very good today."
Carlsson is targeting his first European Tour victory after two runner-up finishes, carded six birdies and a single bogey.
Three-time major winner Padraig Harrington returned a two under 69 matched by defending champion Paul Casey, who dropped two shots in his last six holes to finish one behind playing partner Graeme McDowell.
English teenager Matt Fitzpatrick, who was the leading amateur in last week's US Open, carded a one over 72 in his first tournament round as a professional.
Rory McIlroy could only manage an opening 74, despite the 25 year old having the added incentives of being able to move top of The Race to Dubai and getting back inside the top five on the Official World Golf Ranking with a good performance.
"I still drove the ball great and got in the positions that you need to, but short-sided myself a couple of times, hit a couple of loose shots with my wedges and could not get a putt to drop," said McIlroy, who had carded an approximate 62 in Wednesday's pro-am.
"I was pretty sloppy with the scoring clubs so I might head to the range this afternoon to work on those. I need to do better tomorrow to be here for the weekend."