Cambridge trainer Murray Baker isn't ruling out taking on Australia's best milers with Diademe after she beat a top field of fillies and mares in the Group Three Westbury Classic (1400m) at Ellerslie.

Diademe led from the start for Opie Bosson and kicked clear in the straight, winning by 1-1/4 lengths from three-time Group One winner Final Touch, with top mares Fleur De Lune, Xanadu and Miss Pelear further behind.

Diademe was a $14.10 chance in the Group Three race and hadn't raced since coming third in the Rich Hill Mile on New Year's Day but Baker was confident in her chances with 55kg.

"I thought she'd go very close today at the weights. She's a quality filly," Baker said.

He said the mare was likely to head towards the Group One NZ Thoroughbred Breeders Stakes (1600m) at Te Aroha on April 6 but a tilt at the $2 million Doncaster Handicap at Randwick on April 20 was a possibility.

"She's still in the Doncaster but she'd have to run well in the next couple to think about that. But she's got a bit of class and she's very strong," Baker said.

"Probably Te Aroha looks a good option for her before then."

Bosson described Diademe as "definitely a Group One horse" after the race.

"What she's done on one prep last year was huge and this is a good start to her second prep."

Final Touch ran bravely but found the 4kg she had to give Diademe too much.

Favourite Xanadu, a multiple Group One placegetter who was on trial for the Coolmore Classic (1500m) at Rosehill on March 23, settled handier than usual but despite a favourable 55kg couldn't accelerate and finished seventh.