Australian jockey Tim Clark has claimed his first Hong Kong Group One trophy with an upset win aboard the John Size-trained It Has To Be You at Sha Tin.

It Has To Be You took out Sunday's Hong Kong Classic Cup to make an already special day for Clark even more memorable.

"It's my three-year-old daughter Ellie's birthday. It has been a special day in the past and again today," Clark told the South China Morning Post.

"I'm just thrilled."

Clark has been in Hong Kong since the start of the 2011/12 racing season.

Before leaving for Hong Kong his biggest day at the races had come at Randwick in April of 2011 when he rode a Group One double - the Doncaster Mile on Sacred Choice and The Galaxy on Atomic Force.

He said his first Hong Kong Group One was something he needed to chalk up.

"It's a big moment and was probably the thing I thought I needed to do next in Hong Kong," Clark said.

"But I've been very proud of how my season is going. To be up there in the championship alongside guys like Brett Prebble and Weichong Marwing, top jockeys who have been here for years, feels fantastic."

Brett Prebble also claimed Group One success on Lucky Nine in the Chairman's Sprint Prize.

Prebble will be back in Australia this weekend to reunite with Melbourne Cup winner Green Moon who resumes in the Group One Futurity Stakes at Caulfield.