A move north from his South Canterbury base to Auckland, a change of racing patterns, the rise of the all-conquering forces of trainers such as Mark Purdon and the reality of not having huge sums to play with at the yearling sales meant much of Brosnan's next 30 years was spent working hard without getting close to the lofty peaks of the early 1980s again.
"I was so young then, you think these things come easy, you almost take them for granted," says Brosnan.
"But I look back now and realise I was lucky to have a patch like that. A lot of better trainers than me train their whole lives and never have an open class horse and I had five at the same time.
"Which is one reason winning this final means so much because now I know how rare these moments are.
"The other reason is I get to do this with Emmett. To train an Inter Dominion winner in partnership with your son is a dream."
Brosnan moved to Australia five years ago to spend more time with his adult children, three of who live there, but these days, training horses is more a hobby than a business.
Then along came former age group star Maori Law and the Brosnans worked together on his soundness issues and that, combined with a happy horse and a perfect run in the 3009m race, closed that gap of 42 years to provide another special chapter in Inter Dominion history.
On any normal Inter Dominion night, that would have been the biggest story, but less than two hours later, it was topped by the sensation of Boncel Benjamin being awarded the A$500,000 Pacing Final in the stewards' room.
The former Victorian battler was promoted to first over Expensive Ego, who had led for much of the race but took Boncel Benjamin's line inside the 150m mark, forcing him to come from inside to outside the leader and nearly run him down, missing by a half neck.
After a tense 40 minute inquiry it was deemed the movement of Expensive Ego, the second favourite, cost the 40-1 outsider the race and the placings were changed in the room for the first time in Inter Dominion Pacing Final history.
The result was a bleeding nose for punters but a triumph for young horsemen Jason Grimson and Josh Gallagher with a horse who was battling in poor Victorian races earlier this year but has transformed since joining Grimson's stable.
Favourite King Of Swing faded to fifth after having to race parked, the first four home in front of him having all raced on the marker pegs.
