So I went into it thinking I've got nothing to prove. I am just going to have a fun nationals and whatever results come out of it I will be happy with.
That is a career-defining performance by any standards but what makes Sefton's achievement truly remarkable is that he was so sick with glandular fever over the summer he was unable to train until a few weeks before the nationals.
The New Zealand youth international lacked his usual muscle mass and stamina, with the debilitating condition causing him to doubt whether he could compete at Ohope.
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Sefton admits he went there with no expectations and just relaxed, rather than stressing how he would perform. In the end that may just have been the winning formula.
"I hadn't done the base work throughout the season so building up to nationals I wasn't quite at my peak and was still in that building stage.
"So I went into it thinking I've got nothing to prove. I am just going to have a fun nationals and whatever results come out of it I will be happy with.
"I usually end up being sick at the end of the season because I train so hard and then have that taper period where the body slows down and immune system sort of shuts down a bit.
"With not so much pressure from myself on the expectation of competing well from the whole season of training, it made it more casual, more of a fun thing."
Sefton refused to let his illness beat him over the summer. "I just kept battling away with vitamins and echinacea and all that stuff. Eventually I was able to get four or five weeks of solid training before nationals.
"The other guys had the whole summer of hard out racing and training while I was sick the whole time."
Sefton is a certainty to be one of several Western Bay surf athletes expected to be named in the New Zealand Youth Team this week that will head to this year's world championships in the Netherlands in September.
Before that he has the Australian nationals in April and then winter training to come as he continues to get back into top condition after his illness.