Mrs Crossan agreed to take on Brian down in Ranfurly and sold all the horses she owned and took out loans from family.
The proud owner said her horse was "the only pure breed standing in New Zealand".
The breed originated from Ireland, but Brian was born in Lancashire.
She said he was an all-rounder who traditionally worked on the farm five days a week, but also had to be nimble enough for the farmer to take hunting on Saturdays and then pull the family cart to church on a Sunday.
"When this breed of horse is crossed with a New Zealand thoroughbred you get an Irish Sport Horse," she said.
She said the horse's breed had been on the extinct breed list but was now increasing in numbers around the world.
"I could travel the world and other people would know of Brian, he's that rare."
In 2008 he was one of 60 other horses who underwent testing which included performance tests as well as x-rays.
He was one of just four of those 60 horses graded as a class one which was the highest grade.
Mrs Crossan said Kiwis were becoming more aware of the Irish Sport Horse breed and Brian had sired foals throughout New Zealand.
He had only just qualified for the working hunter competition which he competed in yesterday.
His groom, Lisa O'Neill, said he was performing beautifully before he got to the second to last jump.
"I think he had his sights set on the second jump and fell down on the first."
The rider, Ben Lott, was a bit sore after the fall but Mrs O'Neill said he would be fine.
A team of people had travelled up the island for the event and all wore red bibs to match the red tags on Brian's head gear.
Mrs Crossan said horses did not like being in each other's space so it was a big thing for Brian to enter the ring with others.
"He loves it though, he just loves life. "
