Sydney always turns out at Golden Slipper Day for a carnival of racing but Gai Waterhouse and Tommy Berry added a touch of magic to proceedings on Saturday.

Champion jockey Berry was aboard Waterhouse-trained favourite Vancouver for the $3.5 million main race and started from a wide barrier - a horror position some called it.

But the young jockey, who tragically lost his twin brother Nathan less than a year ago, is no stranger to delivering under the toughest conditions and once again showed how tough he can be.

Berry piloted Vancouver to the lead in the last 100m of the race to give Waterhouse her sixth Golden Slipper - a feat that matches the record set by her father, the late TJ Smith.

Waterhouse said she was driven to win the richest two-year-old race in the world by the last thing her father said to her before his sudden death in 1998.

"He said 'you make a man sick, you can't train the two-year-olds'," Waterhouse said after the race.

"So when he passed away only two days after, I said `I'm never going to let that be my thing' - that was the driving force for me."

Berry added a second Golden Slipper win to his own trophy count after victory in 2013 on board Overreach.

At the 2014 Slipper Berry sobbed during a tribute to Nathan, who died two days before the race after a serious illness.

"It was an emotional day - I don't think I've got any tears left," Berry said before taking the winner's podium with his month-old son, Kaiden, in his arms.

"Even though he's not here, he's the biggest part of my life," he said of his brother.

Nearly 20,000 people came to Rosehill Gardens for Golden Slipper Day, which featured five Group One races and offered a total prize pot of $6.5 million.

A lot of the dressed-up racegoers weren't just there for the horses - their priority was visiting US fashion designer and internet sensation Nicole Richie.

She was the International Ambassador for the day and some of her 4.76 million Twitter followers couldn't resist the chance to see the pink-haired celebrity in the flesh.

Richie, who has built a reputation in the fashion world with her House of Harlow label, had the task of judging the $45,000 Fashions on the Field awards on a panel alongside Myer ambassador Jodie Anasta.

Opting for quiet chic in a short, grey and black animal print Balmain dress, the diminutive star arrived at Rosehill by helicopter and told racegoers she was looking "for what's behind the outfit - the spirit of it".

Regina Thai, a 34-year-old property consultant from Penrith in Sydney's west, caught the celebrity judge's eye with a simple grey frock from Asos and picked up $18,000 worth of prizes.