At $14, Delecta Dreims came into consideration, although O'Fille ($3.50) retained favouritism for Wanganui trainer Wayne Marshment.
After topweight Spiro made the early pace, High Roller took control, followed by Savanah Rush and Sacha, as they went past the grandstand for the first time.
Even Levin's Hoko Gardiner, who co-owns Sacha with wife Nito, was surprised as veteran jockey Darryl Bradley took the mare to the front heading up the back straight, moving to a one and a half length advantage with 850m to run.
But as the field spread three-wide in the straight, Sacha showed she still has some kick and just kept going, holding off Delecta Dreims in a close finish.
O'Fille had to settle for fourth, about fourth lengths behind.
A grinning Bradley said the mare was responding so well under pressure, he rolled the dice to let her go early, easing up a bit with 600m remaining to give her an unlikely shot at the winner's prize.
"It's against plan, she's never led in her life.
"If you get beat you're bagged you win you're a hero.
"She was full of running and just responded all the way up the straight."
For Latta, who said Sacha was adored by her staff, it doesn't get much better.
"At the end of her career, in foal, to get a stakes race with her now is awesome."
Hoko Gardiner collected the cup from supermodel Kylie Bax-Poros and received congratulations from Wanganui mayor Annette Main, who backed a winner.
"To be honest, when she went to the front 1200m out, I was scratching my head," Gardiner said.
"You've got to take your hat off to a senior jockey.
"It's difficult at times, especially if your horse likes following other horses."
Gardiner said he was rapt when Latta nominated Sacha for Wanganui where she had been a previous winner.
He said throughout her career he had never felt the need to take the friendly mare out to his farm because the 7-year-old always loved her stable so much.
"She hasn't got a nasty bone in her body. "She's gutsy a horse that tries her damnedest all the time."
Sacha, born in 2005 by Keeper out of Viva Romance, now has 14 wins from 86 starts with prizemoney of $326,050.
While she has had ups and downs in form, in October last year Sacha won what would be the final Hospice Cup at Wanganui.
She was also successfulin the James Bull Rangitikei Gold Cup at Awapuni in May this year and in July's listed Waikato Stud Opunake Cup in New Plymouth.
The Christmas Races was another success for the Jockey Club, as the on-course turnover of $150,787 for a nine-race programme exceeded the $148,000 of 2012 with 10 races and matched the $150,000 of 2011 for 11 races.
Off-course turnover this year was $1,259,845.