That Tosen Stardom had the ability to win a group 1 was never questioned.

But whether he could achieve that feat remained unanswered until his breakthrough group 1 win in the Toorak Handicap on Saturday at Caulfield.

Having arrived at the Darren Weir stable from Japan with the goal of winning a race that matched his talent and pedigree, he had come close before without saluting.

That's why the trainer took a sigh of relief when Tosen Stardom, ridden by Damian Lane, crossed the line first in the 1600-metre handicap to record Weir's second group 1 for the day, another first for the Victorian trainer.

"It's just a relief that it is done because he is such a talented horse that has been plagued by problems that has got this amazing pedigree to back it up," Weir said.

"It is important that he is a group 1 winner now."

Weir arrived at the track confident that after three runs in relatively quick succession he had managed to get Tosen Stardom fit enough to win a big race.

"The key to today was to being able to get a few runs into him," Weir said.

Lane sensed that fitness as the field straightened with Tosen Stardom travelling so well he couldn't wait to unleash him in the run to line.

"It was a matter of how far when I straightened," Lane said.

"I was getting itchy fingers, getting sick of holding him."

Lane thought the Emirates Stakes at Flemington could be a good race for Tosen Stardom now he has broken the duck and Weir confirmed he would not be tempted to run him in the Cox Plate.

With the group 1 in the bag and the horse fit enough for Weir to move forward with confidence, Tosen Stardom is likely to feature at the front of the big miles in Spring.

"He's got the ability to do it. It's just whether his body lets him do it. He's in great shape now," Weir said.

And he can now run free of the pressure that was slowly building.

"He's a really good horse. He'll make a great stallion," Weir said.