"He's a pretty cruisy horse so I just pretty much sat on him and was a passenger for a really good ride," said a shy and softly spoken Grylls, who started racing last July.
She claimed three kilograms for the 4-year-old brown gelding to take 51kg on the track as opposed to Kaptain Kirkup lugging 59kg to settle in fourth place in the five-horse start.
The Jason Bridgman-trained Gunsmoke (injured) and Glad (opted to go to Ellerslie instead) were scratched.
"He [Kaptain Kirkup] was carrying a lot more weight than I was," Grylls said.
At this stage, any win is a good win for the 20-year-old from Palmerston North. Yesterday she registered two wins, a third and a fourth placing. Her other victory came in race 3, the $7000 New Zealand Bloodstock Insurance for 3-year-olds, when she took the Ralph Manning-trained Little Rocket past the post over 1200m.
Her brother, Craig Grylls, 22, was riding at Ellerslie yesterday.
"I get a little help from him in bits and pieces. He's come a long way in a short space of time," she says, adding the Grylls were "all midgets", with father Gary Grylls a former jockey.
Kurt Hillis, 18, son of Matamata trainers Vanessa and Wayne Hillis and wearing a shocking pink T-shirt that struck a chord with jockey's silks, said the plan was to employ the services of an apprentice to gain a weight advantage.
The younger Hillis said Trentham was a possibility for Have No Mercy on January 19 but he was more likely to be bracketed for a bonus race in Greymouth at the end of the month. The gelding had a hairline fracture on his "pedal bone" of the front leg.
"He's all right now. He's had a bit of time off and is a strong horse who should go up through the grades."
It was an equally productive day for the Hillises, with Michael McNab riding Armadio Estrada to victory over 2100m of the $8000 Windsor Park Karaka Yearlings 2013 in race 4.
The youngster left school at 16 to focus on horses and worked in Sydney last year.
The Hillis-trained Nothing Trivial was second to the Bridgman-trained Single Act in the Russell Stock 1400m race 7.
Hillis said Nothing Trivial might be heading off to Australia.