Three-year-old colt Shamus Award has caused a boilover in the Cox Plate, winning Australasia’s biggest weight-for-age contest to register his first race win.

The Danny O’Brien-trained colt was originally an emergency for the $3 million Cox Plate and only gained a start when race favourite Atlantic Jewel was scratched on the day of the barrier draw.

Apprentice jockey Chad Schofield made all the running, taking advantage of the horse’s light weight of 49.5kg to lead all the way and win by a nose from the fast-finishing Happy Trails.

Last year’s Melbourne Cup runner-up Fiorente held on for third in a great trial for this year’s Cup after taking the race up to Shamus Award.

Schofield, the son of top Sydney jockey Glyn Schofield, became the first apprentice to win the Cox Plate since Brent Thompson aboard Fury’s Order in 1975.

It was also the first Group 1 win for the 19-year-old, something he was desperately keen to capture.

“I’ve been wanting to get a Group One really badly and what a way to do it in the Cox Plate,” he said after the race.

Schofield didn’t have a ride in the Cox Plate until Shamus Award earned a start when champion mare Atlanta Jewel suffered a tendon injury on Wednesday and was subsequently retired.

He was grateful of the opportunity to ride the colt who had run a fast finishing third in the Caulfield Guineas.

“He jumped really fast and I let him find the rail,” Schofield said of the race.

“I knew I had it when I shook off Fiorente and he was just so strong to the line.

“About 100m from the finish line I had a look around and saw Happy Trails flying so I wasn’t sure if we were going to hang on.”

It was the first Cox Plate triumph for Danny O’Brien who had set the horse for the race early in the spring.

He remained confident going into the race despite the horse yet to register a win in its previous nine starts.

Shamus Award was forced back in the Caulfield Guineas and flew home for third but after drawing barrier three in the Cox Plate the plan was to always go forward.

“Today we got a chance to go out and make our own luck and show how good this colt is,” O’Brien said.

“He could have easily been a Guineas winner and a Cox Plate winner, but we’re pretty happy to take the Cox Plate.”