The $3 million Cox Plate is not a bad way to bring up your first Group One victory.

Especially when you are still a teenage apprentice on a horse who had never won a race.

Chad Schofield, 19, who is the only rider to win a Sydney and Melbourne apprentices' title, realised a dream on Saturday with victory on three-year-old Shamus Award in the country's premier weight-for-age race at Moonee Valley.

"It hasn't really sunk in yet but it's a fantastic feeling," Schofield said.

"I've wanted to get a Group One win so badly and what a way to do it in a Cox Plate."

Schofield, the son of Sydney-based jockey Glyn, produced a well-judged front-running ride on the three-year-old, utilising the colt's light weight and at the 200m mark was confident he had the race won.

But then the colt started to tire Schofield wasn't sure he had lasted and even felt he had been beaten by runner-up Happy Trails.

"My heart sank," Schofield said.

"But on pulling up (fellow jockey) Michael Rodd told me that the camera was on me and it was the best thrill of my life."

Schofield started his apprenticeship in Sydney with trainer David Payne where he won the Sydney apprentices' title two seasons ago before moving to David Hayes' stable in Victoria.

He won the Melbourne equivalent last season.