At the front were Steve Cowan, Paul Forrest Rob Gemmell, Darcy Forrester, and Adrian Pettit with Shaun Tucker also in attendance. Behind them, the scratch riders were feeling the pressure, with Bunker, Jason Sturzaker and Adam Gosney best handling the difficult conditions.
The lightweight Bunker attacked his companions on the tough Waitotara hill climb on the return leg and got a gap, scooting away to catch and pass the leaders shortly afterwards.
Passing Maxwell with about 20km left to travel he had about 50 seconds in hand over Cowan and company, with a short gap further back to Sturzaker and Gosney, desperately trying to latch on to the group ahead. Up front, though Bunker had the bit between his teeth and by the top of the climb out of Kai Iwi he had gained more time over his rivals, extending his lead out to well over the minute mark.
Making short work of the climbs, and impervious to the weather, he did more damage on the final climb up Goat Valley.
Behind, Sturzaker and Gosney had shut down the gap to the main group, and added a little more firepower to the chase. Along with Darcy Forrester, these two went clear up Goat Valley and the newly formed trio settled down to try and reel in the flying Bunker inside the final 10km.
Their efforts were in vain.
Bunker was relishing his work and at the finish on Western Line he had extended his winning margin out to a highly convincing 2 minutes 36 seconds over his more experienced rivals.
If he chooses to stick with the sport he should have a bright future. The three chasers tried hard, but were unable to make any impression on the flying youngster, Forrester sprinting clear to take second place from Sturzaker third, with Gosney just behind in fourth.
Forrester's effort was a good one over a hilly course not particularly suited to his powerful build.
In the line-up behind Gosney, Steve Cowan outsprinted Paul Forrest and Shaun Tucker for fifth, sixth and seventh placings, respectively.
A field of eight C-grade riders raced the 36km to Maxwell and return for the Paddy O'Brien Memorial Cup and it was Scott Francis who scored his maiden win in great style.
Francis, older brother of former top competitor Tom, caught the front-markers by the turnaround at Maxwell then ripped into his work with benefit of the tailwind home to clear out by just over two minutes. He also easily clocked the day's fastest time. Heather Johnstone battled on to head off Tamara Ross for second, with Ross third ahead of Michaela Walker a solid fourth. Stu Bruce put in a good ride for fifth off scratch after losing his co-marker Brian Hayward to a puncture.
Stefan Bourke boxed on for sixth, with Debbie Cain coming home seventh.