Tanner's coach, Craig Kirkwood, says middle distance running, which holds fabled status in New Zealand sports lore, is still popular.
"The history New Zealand has with medals on the global stage – people appreciate that. Every young kid that has run has had a crack at a 1500, it is pretty popular event."
He says Tanner's form has been good and he hopes to see it continue.
"I think it is just the time he has had in the sport and his natural progression. You can only go so far on hard work, you have to have some natural ability as well. We watched his race on a live stream and we had the plan going in knowing it would go about 3.35. The plan was to be a couple of seconds slower through splits and hang on for as long as he could."
As well as setting a new personal best Tanner was rapt to get time on the track where he will be doing most of his sessions when he takes a scholarship at Washington in September. It added to what has already been a stellar 2019, which has included breaking Nick Willis' under-19 record and winning the national 1500m title.
"I can't be complaining, I have been setting these goals and achieving them," Tanner says.
When I go [to Seattle] in September it will be cross-country season and that will be a really good build phase for me. The ultimate goal is the Olympics and I will need to win races and get fast times."
An important part of that process is next week's Oceania Athletics Championships in Townsville, where Tanner will race on Wednesday afternoon.
"To win an Oceania title as an 18-year-old would be surreal and Oceania is really important for Olympic qualification."
A sub 3.35 time will earn a spot at Tokyo next year, and anything outside of that will rely on rankings, which the Oceania event contributes to.
"A week ago I would have said it [sub 3.35] was an extreme long shot, now it is more probably an outside shot – but achievable."
Sam Tanner's next race:
Oceania Athletics Championships
June 25-28
Townsville Sports Reserve
Townsville, Queensland