A historic day at Randwick came to a close on Saturday with brothers turned co-trainers Ben and JD Hayes claiming their first Group 1 together in the $3 million Doncaster Mile.

The young duo combined with Mr Brightside in the final feature on the program, an upset that caught plenty off guard as the $21 pop drew clear out wide over the final stages to beat I’m Thunderstruck and Icebath right on the line.

The Kiwi galloper was having his fourth run back after running fourth in the All-Star Mile two weeks earlier, but largely went unwanted in betting with no heavy track form next to his name.

“I’m not saying he loved the track but every time I urged him along and asked him to extend he really responded for a horse that really wasn’t that comfortable in the ground,” winning hoop Craig Williams told Sky Racing.

The four-year-old had finished no worse than fifth in each of his 12 career starts leading in, however, while his form over the mile also read well: five wins from eight starts.

A patient steer from Williams proved the difference in the end as the winning jockey also claimed his first Doncaster.

“They’re the future. When they come into the yard today, Sydney’s biggest race on the first day of The Championships, as young trainers they just said ‘we’ll leave it up to you – tricky barrier draw,” Williams said of the young co-trainers.

“But they just said this horse is going better than he’s gone this whole prep. So they give me the confidence and then we have to trust the horse and through their hard work and education and their processes that’s the end result, they won a Group 1.”

I’m Thunderstruck was game in defeat, finishing runner-up for the second race in a row after landing 1.5L off Zaaki the start prior in the All-Star Mile.

Icebath was genuine as always for third, while the favourite Forbidden Love only got going late with next to no weight on her back.