Alonzo's two and a quarter-length victory in the 1m5f maiden completed Joseph O'Brien, the trainer, with a trifecta at Sligo.
On his last run, the son of Frankel finished fourth at Cork, second to stablemate Bladon. He then took the lead on the approach to the straight and held strong to hold off Man of Worth's charge.
Following Intellotto thirty minutes before, Dylan Browne McMonagle, wearing the colours of Sun Bloodstock, made a swift double.
The Letterkenny rider reported: "He did it well. I jumped from the gates well. Declan (McDonogh, on Bladon) was quicker than me on my inside so I was happy to take the lead off him and use him as a target. My lad switched off. He was entitled to do that, I thought, as it was a nice maiden in Cork and he ran a blinder. He's come forward plenty, got to the line well and will be a nice stayer hopefully. He's very well bred so fingers crossed."