Star Kiwi mare completes undefeated campaign with Flemington Group 1 win.

A different venue and more accomplished set of rivals posed no problem for Imperatriz, who completed an unbeaten Victorian spring campaign in Saturday's Champions Sprint at Flemington.

The flying Kiwi mare took her career Group 1 tally to eight when she held off The Everest runners Buenos Noches and In Secret to win the $3 million event.

The victory followed Group 1 wins in the Moir Stakes (1000m) and Manikato Stakes (1200m) at The Valley, having started the campaign with victory in the Group 2 McEwen Stakes (1000m) at the same venue, and trainer Mark Walker was left to try and find more superlatives after his first Group 1 win at Flemington.

"She's a real star and did the whole of New Zealand proud today," Walker said.

"It's probably a little bit of relief more than anything.

"You dream of days like this and there's a lot that goes into these days from the ground up."

Imperatriz jumped well in the 1200-metre event and followed leader Front Page, before Opie Bosson popped off that gelding's back at the 400m and cruised to the lead at the 300m before quickly putting two lengths on her rivals.

Buenos Noches charged at the daughter of I Am Invincible over the final furlong, but $2.15 favourite was holding that $14 chance at the line and scored by half-a-length.

In Secret ($3.50), last season's Coolmore Stud Stakes and Newmarket Handicap winner over the Flemington 1200m, was three-quarters-of-a-length away third.

"I was expecting Asfoora to slot forward but she took a hold, so I used Front Page as my bunny and I probably got there a bit soon," winning jockey Opie Bosson said.

"Geez it's a long way up that straight. But to her credit she knuckled down and put her ears back.

"We always knew she was really talented, she's just getting better with age and she is the real deal and she has proven it now."

Imperatriz has now won 17 of 23 starts, with a narrow Canterbury Stakes defeat in March the only time she has been beaten in nine starts this year, and the Te Akau Racing team is now contemplating taking on the world.

"I'd love to, I'd love a trip away," Bosson said.

"It'd be nice to get to (Royal) Ascot and show them how good she is."