"I could never beat my mate, so one day we swapped ponies and he still won, at which point I realised I was never going to be a champion jockey."
What Fieldes couldn't have known at the time was that his mate, a young Brent Thomson, was going to win four Cox Plates and become one of the world's finest jockeys.
"All I did was win 10 eggbeater [amateur riders'] races over a very long time.
"Today, what James McDonald does in a week took me 25 years to achieve. That's when you realise how good some of these riders are."
If Alexander Fieldes was restricted to eggbeater class as a rider, as a horseman his attributes rate somewhere around superb.
He was given Marea Alta to train after she had just finished at the back of the field in a 2000m maiden at Stratford on New Year's Eve.
There are weaker races, but not many.
If he had got the mare off a one-horse amateur and improved her to win five races in quick time since April 13, including her past four straight, it may not occasion great surprise.
But Fieldes took over from Awapuni trainer Mark Oulaghan, as good a horseman as we have in New Zealand.
"I've done a few things differently," says the ever-humble Fieldes.
The first thing he did was call Cambridge trainer Shaune Ritchie.
"Shaune had Roi d'Jeu going so well and I figured he could perhaps give me some advice about how he got a Montjeu going so well.
"Typical of many of them she is a big, skinny thing with no brains that doesn't do that well.
"Shaune said the first thing to do with a Montjeu is back off them - they don't take work.
"The hardest thing to do is not gallop a horse when everyone around you is galloping theirs, but that's what you have to do."
Fieldes said he was embarrassed by Marea Alta at Te Rapa. "When she arrived off the float [from Wanganui] on Friday she wouldn't eat and broke out in a big sweat.
"On race morning, it took me two hours to get the sweat off her and to shampoo her and the minute I started saddling her she broke out in this massive sweat again.
"Thank goodness there were only seven people watching the horses in the parade ring." (Something of an overstatement - there was a good crowd on Saturday).
Fieldes trained winners before 1990, but because of an archaic rule at the time that stipulated if you rode as an amateur you couldn't hold a professional trainers' licence, they were in his father's name, and in others.
His first official victory came with Earlybird at Hastings on January 1, 1990. The rider was Noel Harris.
Twenty-one-and-a-half years on it was Harris again who Fieldes legged into the Marea Alta saddle on Saturday. And he did the job beautifully.
"She wasn't handling the heavy ground on the inside, so I pulled her out wide," said Harris later.
"ARA [Alexander Richard Aden] told me not to worry if she came off the bit, because she always hits a flat spot in her races."
Harris is a genius on late-finishers and Marea Alta swamped the leaders to win comfortably.
Fieldes, a meat inspector, never trains more than four horses at a time and since Saturday's race has already turned down another Montjeu horse.
