The Awapuni trainer produced the stable favourite for an upset win in the Cambridge Stud Zabeel Classic (2000m) after five previous placings at the highest level, two of them in past editions of the Ellerslie weight-for-age feature.
"It's just an absolute buzz," Latta said. "He's a lovely horse and he so deserved that. It's been a great day for us."
She was on course at Awapuni where she celebrated a winning treble with That's Amore, Lincoln's Gal and Denny's Lincoln.
Latta also pulled off a masterstroke by engaging Trudy Thornton to partner the eight-year-old Authentic Paddy.
"He needs a strong rider and Trudy does exactly what she's told," she said.
Thornton got away with easy sectionals in front and Authentic Paddy did the rest, comfortably holding the challenge of Lizzie L'Amour at bay in the straight to score by a length and a-quarter.
Volkstok'n'barrell claimed third ahead of the defending champion Consensus and Benzini.
"It's amazing, he knows his job and he's a pleasure to ride," Thornton said. "I just want to thank Lisa and the owners for the ride."
With Thornton able to dictate a sit and sprint race on the Howbaddouwantit gelding, the favourite Hiflyer had no chance from back in the field and he ran eighth.
The Zabeel Classic also marked the final appearance of the Gr.1 Australian Oaks (2400m) winner Sofia Rosa.
There was no fairy-tale end for the mare, who is in foal to Savabeel, and she finished seventh.
A half-sister by Tavistock to Authemtic Paddy will be offered at the 2018 NZB Premier Yearling Sale by Goodwood Stud as agent as Lot 47.– NZ Racing Desk.