Robert Rock turned in 31 to open up a one-shot lead as the fourth Rolex Series event of the season got under way at the Dubai Duty Free Irish Open hosted by the Rory Foundation.
The Englishman is a two-time winner on the European Tour but has just one top ten this season as he goes in search of a first victory since 2012.
He is playing in a fourth consecutive Rolex Series event as the European Tour stages a huge run of events in the summer, and four birdies on the front nine moved him to four under, one ahead of England's Ashley Chesters, Kiwi Ryan Fox and Frenchman Adrien Saddier.
There was then a group of five players at two under as Ballyliffin Golf Club presented a gorgeous setting on its Irish Open debut.
Rock got off to a fast start, making gains on the first, second and fourth to join the lead and when he holed a 15-footer on the ninth, he was ahead on his own.
Fox already has four top tens in Rolex Series events and he made birdies on the 13th, 14th, 17th and first to go with a bogey on the 15th in his first ten holes.
Playing partners Chesters and Saddier were both bogey-free in their first ten holes, with Chesters picking up shots on the fourth, sixth and seventh, and Saddier making gains on the third, fourth and tenth.
Belgian Knockout champion Adrian Otaegui, AfrAsia Bank Mauritius Open winner Dylan Frittelli, Ryder Cup star Andy Sullivan, Qualifying School winner Sam Horsfield and Challenge Tour graduate Erik van Rooyen were all two shots off the lead.
Defending champion Jon Rahm was in the group at one under alongside last season's runner-up Matthew Southgate and 2014 champion Mikko Ilonen.
England's Mark Foster made the 20th hole-in-one of the season at the par three seventh, holing a seven iron from 177 yards for the 36th ace in tournament history.
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