He said running a stable that trains many horses he and co-trainer Grant Cullen, who has group honours, often sold pedigree horses before they were at their prime to compete in elite races.
"I have only raced a handful of group ones in my time."
Lowry had "a quiet feed" with Irish Fling's owners, Pak 'N Save Syndicate, to celebrate the momentous occasion on Saturday night.
"It's a great team effort from our stable back at home.
"It's not about one person," he said.
It was a great day for Hawke's Bay because good friend and trainer John Bary also clinched a group one quinella. Du Plessis again capped off a good day at the office on Recite in the Ocean Park Levin Classic two races before Lowry, finishing half a length ahead of stablemate Franzac to pocket $140,000 and $46,000, respectively.
Both Irish Fling and Recite are daughters of stallion Darci Brahma, the resident stud at Oak Stud, Cambridge.
Bary was quick to reinforce Lowry's winner capped off a Super Saturday for the Bay trainers.
"Guy's a mate of mine so I'm really thrilled for him," he said of Lowry, adding it was in his nature to be placid about everything.
Lowry said Irish Fling had won the "toughest sprint race in the country".
"It's a straight six. It's like sprinting over 1300m so that's what makes it tough," he said as the mare won $250,000.
It was her fifth victory from 15 starts.
Irish Fling finished fourth in her open class debut in the spring before she went south to Riccarton where she won the Listed Pegasus Stakes and backed up four days later to run third in the Gr.3 Stewards' Stakes.
He lauded Du Plessis for a patient ride.
"They broke the 1.8 mark which is a brilliant fast time," Lowry said, claiming she is the most-improved sprinter in New Zealand.
Bar 3-year-old Bounding, every other favourite was in the line up.
"I just want to see how she pulls up because it was a pretty firm Wellington track so we'll work on a plan for her in Australia," he said, adding he would take her to Sydney in April for the $A2.5 million (NZ$2.65 million) 1200m TJ Smith sprint.
Recite has taken her earnings close to $400,000.
"We've got no plans for her right now," Bary said, revealing the filly was "still weak and not 100 per cent".
Former All Black Zac Guildford has shares in (25 per cent) Franzac with maternal grandfather, Frank Burt (50 per cent) and Christchurch friend Wayne Hicks (25 per cent).
The gelding will now head off to the $750,000 New Zealand Derby at Ellerslie, Auckland, run on March 1 with stable mate Miss Selby.
Bary-trained and Richard and Liz Wood-owned and bred Jimmy Choux won the derby, worth $2.2m, in 2011.
Bary likened the more than a century-old derby to a Melbourne Cup type of race in New Zealand.
He saluted Danielle Johnson, who rode a fantastic race on Franzac, for taking the pace off the mid-stages.
"It's also a huge thank-you to my staff - what a great result."