Curran, from Dublin, finished runner-up at one-under 287 after rounds of 70-76-69-72, while Simon Ward and Robbie Cannon shared third at one-over.

Keating, a University of Louisiana at Lafayette graduate, carried a two-shot lead into the final day after opening rounds of 71 and 69 helped him reach three-under through 54 holes.

What looked like a comfortable path to victory quickly turned into a battle. Keating opened the final round with a bogey before a triple bogey at the fourth and a double bogey at the seventh suddenly dropped him behind Curran, who was making a charge with aggressive play of his own.

Curran seized the momentum early in the round, making an eagle on the par-5 second and adding another birdie at the third to move into the lead as Keating struggled on the front nine.

But the championship swung again around the turn.

Keating steadied himself with birdies at the ninth, 11th and 12th to pull level heading into the closing stretch, separating himself and Curran from the rest of the field.

The decisive moment came late. Curran dropped a shot at the par-3 16th, and minutes later Keating responded with the shot of the tournament at the 17th, driving the green before converting the birdie putt to regain the outright lead.

A closing par at the 18th secured the biggest win of Keating’s amateur career and continued his impressive run at Royal Portrush after winning the Ian Bamford Scratch Trophy there earlier this summer.