George Kent's Custom Cut caused a 25-1 upset under Ronan Whelan in the feature race at the Curragh, the Big Bad Bob Gladness Stakes.
Despite going on a fine run in handicaps last summer, this Group Three looked a little too much on paper for the gelding after he beat only a handful home in the Irish Lincolnshire on his most recent start.
But he proved an impossible horse to pass in front, and while Aidan O'Brien's long-absent Nephrite made a pleasing comeback in second, he was held by half a length, with La Collina a further nose away in third.
It was the biggest winner to date for champion apprentice Whelan, who told At The Races: "He likes his own way out in front and just kept winding it up and winding it up. Things didn't go to plan in the Lincolnshire, but he scoped badly and you can rule that one out."
The winning trainer's son and assistant George Kent jnr commented: ""I said coming here that it was a fact-finding mission, so that tells us where we are at. We were not too worried by his run the last day. He showed in his work he could be competitive at this level and it's great he got the job done.
"It's great to have this type of horse for a small yard. We need a horse like him. There's a lovely programme for this type of horse. He had to make the step up today and thank god he did. He's never let us down. He didn't mind that ground today. It's onwards and upwards."
Whelan maintained his flying start to the Flat season with a double as he got the Patrick Prendergast-trained Tantalising (4-1 co-favourite) home in the Irish Field Handicap, holding the fast-finishing Fantasy King by a neck.
The trainer said: "I'm delighted with that. She picked up a lot of cheques last year as she was placed a lot. I was wondering was she ever going to get her head in front.
"She was working well, but I was a bit concerned about her being ready as she was heavier on the scales, but she's more of a mare this year rather than a filly. She's by Sadler's Wells, so she'll make a nice broodmare. We'll have to try and get some black type as it would make her very valuable."