Booker upset favourite backers with a determined victory in Sunday's Group II Thousand Guineas Prelude (1400m) at Caulfield.
Punters backed last season's Blue Diamond Stakes winner Catchy into odds-on but were left lamenting after a positive ride from Dwayne Dunn aboard Booker.
Settled in second place on the quarters of Mahlani to the home turn, Dunn kicked Booker ($6.50) into a clear lead early in the home straight and while getting tired close home had enough in hand to hold the late finishes from Shoals ($5.50) to score by a neck with Catchy ($1.95 fav) a short head away third.
Mathew Ellerton, who trains the winner in partnership with Simon Zahra, said he thought Booker had earned the win the hard way.
"She did a bit of work early but we were always intending to be positive," Ellerton said.
"She was getting a bit tired towards the finish but she did well to hold on.
"She's a filly that doesn't get put under pressure at home and I think she's still learning how to let down."
Booker had placed both her starts this preparation at Group level and Ellerton said the daughter of Written Tycoon will now head to the Group I Thousand Guineas in two weeks time.
"That's where we will go, she probably didn't want it too much further today but she did do all the work early," Ellerton said.
"I'd say she's still got some improvement in her both fitness wise and race smarts."
Dunn echoed those sentiments.
"She's a lovely filly and hopefully she can win the Thousand Guineas," Dunn said.
"She had to do it hard early and then found for me early so she should have some improvement there."
BOOKER fights off Catchy and Shoals to land the Thousand Guineas Prelude. #RacingLivepic.twitter.com/llKDK2c5lg
— Racing.com (@Racing) October 1, 2017