Perth racing has a new star with three-year-old filly Perfect Reflection winning the Group One Kingston Town Stakes at Ascot, the final Australian Group One race of the year.

The Bob Peters-owned Grant Williams-trained Perfect Reflection retained her unbeaten record and became the first filly to win when she beat stablemate Delicacy in a photo-finish to the 1800m-race.

Leading jockey Willie Pike chose to ride Perfect Reflection at 50kg and his decision was vindicated.

"I went too early but she was bolting and going so well," Pike said.

"I had no hesitation in picking her as my ride."

Punters followed Pike's lead and sent Perfect Reflection into the race as the $4.40 favourite with last season's champion three-year-old filly Delicacy at $5.

The margin between the pair was a nose with Dark Musket ($151) third, another 4-1/2 lengths away.

German horse Magic Artist ($5), fourth in two Group One races during the Melbourne spring carnival beat just three runners home.

After a heavy storm earlier in the day, the track was in the heavy range.