"I was very impressed. He could have won by a lot more. He jumped well," Gillies said.
"He was stepping up in distance and I am confident about his stamina."
The Cambridge-based Gillies was riding Daatldomee for the first time and the Istidaad gelding won by eight lengths over 4280m.
Daatldomee had won a 3300m maiden steeples at Oamaru at his previous start on June 30. Gary Walsh, who rode Daatldomee at Oamaru, opted for Zador yesterday, but he was injured at Trentham and replaced by Ross Doherty. Zador finished fourth, 18 lengths from Daatldomee.
Daatldomee, owned and trained at Rangiora by Jean Schluter, ran second to Lizac in the Homeby Steeples (3300m) at Riccarton last month.
The Koral is over 4250m on August 6 and the National over 5600m a week later. Gillies has ridden over Riccarton country but not in those races. He rode Mr Charlton to finish second to High Season in the 2009 Grand National Hurdles.
Gillies also won the restricted open hurdles yesterday on Borrack as substitute for Cody Singer, who had a mandatory three-week stand down after sustaining concussion at Oamaru on June 30.
Borrack is unbeaten in three starts over hurdles. Singer is employed by Adrian Bull, the Hunterville trainer of Borrack.
Butch James, a stablemate of Borrack, easily won the maiden steeplechase yesterday in the hands of replacement rider Cory Perrett.
Jo Rathbone, the declared rider for Butch James, sustained severe bruising after a fall from Belinus in the maiden hurdles yesterday. She underwent X-rays at Timaru hospital and returned to the track later in the day.
Rathbone won the Wellington Hurdles on Honey and a maiden hurdles on Gioarchino at Trentham on Saturday. Both horses are trained at Wanganui by Kevin Myers. He races Gioarchino with Marion and Drew Stevenson, of East Taieri.
• Ishiabeel repeated her win of last year in the Winter Cup Trial yesterday and gave trainer Terri Rae her fourth successive win in the race.
Rae also won with Don't Say Clang in 2008 and 2009. Don't Say Clang was scratched yesterday when he did not satisfy Rae with his condition. He had finished second to Flying Alibi in the Winter Cup Trial at Ashburton a week earlier.
Don't Say Clang will now be considered for the Winter Cup Trial at Waterlea next Sunday or a 1400m race at Oamaru the following week.
Ishiabeel and Don't Say Clang are set to clash in the $100,000 Winter Cup (1600m) at Riccarton on August 6.
Don't Say Clang ran third to Taking The Mickey and The Twist in the 2009 Winter Cup. Ishiabeel finished 12th last year when the second favourite.
