Vink's attack came after he dropped Jeremy Vennell on the penultimate climb up the testing Dyers Pass hill to open up a 45 second buffer with a lap remaining.
"I would have liked Vennell to stay on for longer but at the bottom of the climb he said he was gone," Vink said. "So at that stage I had no choice but to go solo and time trial my way to the finish."
Pre-race favourite Jack Bauer, about to begin his World Tour career with Garmin Cervelo, made the initial charge from the pack, but it was Bevin and Williamson who took up the chase. Vink's margin was reduced to 35 seconds at the top of the climb and cut to just 12 seconds at the 1km mark, but Vink managed to hold on to record the win.
"This win means a lot to me, not just that I won but how I won it," he said. "It has given me a lot of confidence because I know I can win this level of race now. The national champs are always tough and fast races because there's no prize for finishing second.
"I knew the chasers would be coming at me but at that stage you can't worry about them. It was a matter of putting your head down and giving it everything you have. If it was good enough then it was good enough."
The pace was on from the start today, with riders recording speeds of up to 60km/h, before a group of nine made the first break. The group, including former Olympian Robin Reid and newly-crowned New Zealand road cyclist of the year Jesse Sergent, pushed out to a 1m38s lead at the halfway mark, but were eventually reeled in.
Taranaki's Michael Torkler, Vink and Vennell then pushed clear, before Vink turned up the heat on the penultimate lap to score the ultimate reward.
Vink will prepare for the New Zealand cycle classic in the Manawatu race later this month with his Mico Protrain team, before heading to Belgium where he will race for a top amateur team.
"If I can get some good results I hope this will lead to a professional contract. The team have some great race starts around Europe in some top stage races."
Results, RaboDirect National Road cycling Championships, 183km:
Elite: James Williamson (PureBlack Racing) 4:38:15, 1; Jeremy Yates (Mico Protrain) at 1:49, 2; Jeremy Vennell (Team Bissell) at 2:04, 3.
Under 23: Michael Vink (Mico Protrain) 4:38:09, 1; Patrick Bevin (Team Bissell) at six seconds, 2; Josh Atkins (Canterbury) at 22 secs, 3.