Star jockey Jamie Kah proved the key to coaxing the best out of the enigmatic Nature Strip when she combined with the superstar sprinter to win the Black Caviar Lightning.

The race proved to be a triumph for Australia's leading trainer Chris Waller, who produced the quinella in the Group One at Flemington with his three-year-old filly September Run flying home for second.

Kah was emotional after the win, her fourth at Group One level, and said it was an honour to be given the chance to ride a horse of Nature Strip's calibre.

"To get on a horse like him, and for Chris Waller, is something I couldn't imagine and to get the job done is amazing," Kah said.

Waller turned to Kah when James McDonald told the trainer he didn't want to travel to Melbourne because of COVID-19 concerns.

Kah partnered Nature Strip in a recent Flemington jump out where she got him to settle and she did the same in Saturday's 1000 metre sprint.

She positioned Nature Strip second, behind race leader Pippie, and he travelled perfectly throughout the run.

Kah said she just let Nature Strip do his thing.

"Pippie set a nice, hot tempo and he actually relaxed and dropped the bit," Kah said.

"They're going to do that when they run that quick but it just set up beautifully for him. He wanted to drift in and roll in a bit late but I didn't really care."

Kah said Nature Strip was in a good mood, as he was when she trialled him.

"They've found the key to him first up, given him that extra trial and he has to be rock-hard fit to run because he runs at such a high cruising speed," Kah said.

The Black Caviar Lightning was the six-year-old son of Nicconi's 15th win from 28 starts and his fifth at the highest level.

The victory completed a treble for Kah, who scored earlier wins on Quantum Mechanic and Zou Dancer.

Waller watched the race from Randwick and was thrilled to see Nature Strip return to his best after a frustrating spring when a cluster of things went wrong.

"It was satisfying. We've made everybody aware that he was hard to get right in the spring and a few things went against him in his races," Waller said.

"A horse like him needs everything to go right.

"It was a well-judged effort and it's good to have him back."

Nature Strip ($4.40) defeated September Run ($10) by a half-length with another three-year-old filly, Swats That ($17), 1-1/4 lengths away third.

The disappointment in the race was short-priced favourite Bivouac who finished fourth.

His jockey Glen Boss was satisfied with the effort but thought he raced a bit fresh in the early stages and settled closer than he expected.

"That's his first run so he'll improve. He's a big colt now so he's going to take a lot out of that," Boss said.

Craig Williams said September Run was "amazing in defeat".

Waller confirmed September Run would stay in Melbourne for the Newmarket Handicap while Nature Strip could join her in that race, or return to Sydney for the Challenge Stakes and T J Smith.