Because of concerns over his knee, Eyles originally planned to just run through the race from his 17min handicap and treat it as a training run as he builds up towards a 12-hour adventure race in Dunedin in early November.
"I've had cleats fitted to my bike and I'm not used to them, which seems to have sparked a bit of knee trouble," he said.
Eyles (28), who is an environmental manager and in his second year of competitive running, slipped under the radar a little as a pre-race prospect.
Although preferring the longer form of running, he finished sixth in the Three Peaks event earlier this year.
And before that, a liking for the Papatowai Challenge course resulted in his gaining a series of 10th placings.
"Perhaps running over my home turf helped me a bit today," Eyles said of living in Sawyers Bay.
He trains over the terrain regularly and often incorporates Grahams Bush into his running.
"I knew when to push it and when to ease up a little," he said.
Buoyed by encouragement from wife Kristy, outside the couple's Brickhill Rd property, Eyles first came into contention at Burkes, when he appeared to be the best of a bunch running through 6min behind race leader at the time, Carol Chettleburgh (Hill City-University).
Chettleburgh had just run down Peter Smith (Civil Service), who had held the lead since Sawyers Bay.
With the field closing in on Chettleburgh, it was Eyles who came off the hilly part of the course in the best condition, hitting the flat section of the course from Ravensbourne with the front of the field in his sights, to take over the lead opposite Moller Park.
"I just straight-lined it for the finish."
Eyles finished with a time of 49min 7sec for the 12km course.
Second to cross the line and, continuing something of a family dynasty in the event, was Kirsty O'Sullivan (Hill City-University), who won the trophy for the first female to finish.
For O'Sullivan, nee Morris (26), a natural hazards analyst for the Otago Regional Council, it was the second time she has won the women's trophy in the event. She first won it under her maiden name in 2008.
Her mother-in-law, Sue O'Sullivan, was the first woman to win the event outright when it was opened up to include female competitors in 1983, and father-in-law Danny O'Sullivan won the trophy in 2000.
Kirsty was making the most of her second victory in the women's section of New Zealand's oldest road race, first held in 1902.
"I may never do it again," she said.
Kirsty was made to work for her title on Saturday, after being placed on the same 18min 30sec handicap marker as middle-distance track champion Shauna Pali.
"The pace was pretty solid early on," she said.
With Pali fading coming off the hill stages, it appeared O'Sullivan might threaten for the lead and emulate the feat of her mother-in-law 19 years earlier.
As she hit the Ravensbourne straight she could see Eyles ahead of her, but became aware over the final kilometre the gap was too great and that Eyles was putting in the after-burners. She ran on to finish 18sec behind Eyles.
Matt Gibbons led the remainder of the field home to clinch third in 44min 7sec. That was good enough for third-fastest time behind Mike Wakelin (Hill City-University), with the fastest time of 42min 6sec, and Neale McLanachan (Leith), second-fastest in 42min 34sec.
Matthew Ogle (Hill City-University) won the junior men's 4.4km event in 16min 37sec and Hanna English the junior women's in a smart 15min 55sec.
