A last-to-first finish from Maryore has given Canberra's Philip Courtney the biggest thrill of his short training career in the rich Provincial Championships Final at Randwick.

The 65-year-old Courtney took up training about five years ago, firstly as a hobby until going full-time with eight horses currently in work.

The stable's biggest win before Maryore swamped her rivals in Saturday's $390,000 1400m race was the same mare's victory in the $150,000 heat of the Provincial Championships series staged at Goulburn last month.

Sent out a $20 chance on Saturday, Maryore was settled at the tail of the field under jockey Tim Clark before she unleashed her winning run down the outside.

Maryore swept past leader and $2.45 favourite Pomelo passing the 100m and drew clear to beat Better Not Blue ($11) by three lengths with a short half-head to Ziganui ($26) third.

Pomelo was overhauled by the minor placegetters late to finish fourth.

"It's a big thrill," Courtney said.

"The biggest day for our stable. The biggest day for the owners, and we're pretty stoked because we planned this.

"And when plans come off, it makes it even sweeter.

"We get our winners, but this is a shot in the arm for us all, I can guarantee you," Courtney said.

Courtney felt Maryore had been underestimated but he said Clark knew the five-year-old needed to be ridden quietly and saved for one finishing burst and was confident if the speed was on she would finish strongly.

"I was jumping up and down too much to really see it," he said.

"As soon as she got to the front I knew it was over."

This is the third year of the Provincial Championships but this was the first time Canberra-trained horses have been eligible to compete.