Pride Of Pimlico stuck on well to come out on top against fellow two-year-old newcomers in the Irish Stallion Farms EBF Maiden at Naas.
Brendan Duke's son of Casamento was always up with the pace before being asked to go and win his race by Ronan Whelan.
Pride Of Pimlico pulled clear in the final half-furlong to spring a 20-1 surprise in the first race of the Irish turf season, beating Eagles Rock by two lengths.
"He must be a really good colt. He's done miles and miles of cantering, but we've never revved the engine," said Duke.
"I was horrified by the carry-on of him beforehand, I can't believe that. He's definitely talented and loved the ground.
"He's from a good family, that's four from four for the mare and she won five herself, including twice as a two-year-old."
He added: "When I give ten grand for one they really need to be group horses! He'll progress and we'll take our time with him.
"Today was a big day for him. I'm a bit disappointed with the before race carry-on, but I think he's a very nice horse.
"Ground definitely helped because he was very fit. It's a great tribute to the lads at home and how hard they've worked."
Katie Cruel (7-1) justified strong late support to open her account in the Kildare Post & Kildare Now Maiden.
The Alan Fleming-trained filly had finished a close second on her only previous start over the course and distance in November, when a 25-1 chance.
She showed that was no fluke as she went one better in the hands of Chris Hayes, beating Aidan O'Brien's 7-2 favourite Hence by half a length.
"Chris was happy with her and thinks she's quite nice," said Fleming. "There's still a bit of improvement to come, he reckons, and she'll come on a good bit from the run.
"I'm not sure where she'll go now. She is for sale and if she's not sold obviously we'll have to go again.
"If we do go again it'll be in a black-type race somewhere to add a bit of value. We do think quite a bit of her at home and she's done it there today."
Medicine Jack (5-1) overcame a 302-day absence to land a narrow success in the Naas Racecourse Launches The 2018 Flat Season Handicap.
The Ger Lyons-trained four-year-old showed no signs of race-rustiness as he gained the upper hand close home in the hands of champion jockey Colin Keane, scoring by a head from Smash Williams.
"The horses are as fit as we can have them at home," said Lyons.
"Part of me didn't want to run him and the other part said well we've had all of last season off. We literally couldn't get him to raise a gallop at home.
"He was a Group Two winner, but we gelded him at the end of the season and kept him going. His work was OK but was like we were seeing at two, without getting carried away.
"The only box we didn't tick today was the heavy ground, but my theory is once they turn four I'm running them and if they don't handle it we won't ask them to do it again."
He went on: "The wheels are back on the wagon and we'll probably aim for that Listed race in Navan (Cork Stakes on April 7). We'll see what the handicapper does and we'll tread lightly.
"If he gets back to any semblance of what he was at two we'll have fun with him this summer."
