A 19-year-old who dreamed of being a jockey as a little boy has combined with a "retired" racehorse to break a century-old record in the $1.25 million Newmarket Handicap.

Regan Bayliss was almost lost for words after winning his first Group One race only three months after finishing his apprenticeship on Saturday.

"This is all I've dreamed of. I don't care about anything but horse racing," he said.

Retired Hong Kong galloper Redkirk Warrior became the first horse to win the famous Flemington Group One sprint in its first race after a spell since Polycrates in 1917.

Hall of Fame trainer David Hayes had been singing the gelding's praises, despite it being his first start since November after undergoing a throat operation and the work it took to fix the hoof problems that led to his retirement from racing in Hong Kong.

"It's a big ask to win a Newmarket first-up," said Hayes, who now trains in partnership with son Ben and nephew Tom Dabernig.

"But I've told anyone who cared to listen he's probably the best horse in our stable and I think he proved that today."

Hayes was also full of praise for Bayliss.

"He is a class rider, a star of the future."

Bayliss started riding when he was a little boy, mustering cattle on his grandfather's farm.

He was 13 when he moved to Melbourne from Queensland with his jockey father Jamie and older brother Jake to pursue their racing dreams.

"I'm a little bit impatient. I've been waiting for this day for a very long time," Bayliss said.

"I just can't believe it."

Saturday's other major Flemington race, the $1.5 million Australian Cup, went to Melbourne Cup-winning trainer Darren Weir.

As well as being his seventh Group One of the season, the win was extra special for Weir who owns a half share in Humidor with his stable clients.

"It's been a great ride for the new owners, hopefully a good ride for the previous owners as well," Weir said.