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The 26-year-old Cantabrian made the torturous 12km Coronet Peak climb at the end of a 138km stage from Mossburn to Queenstown yesterday look like an escalator to take a 1min 20sec lead overall at the midway point of the race.
"The key today was having an easy ride the last two days. The team has looked after me so so well and I hit the bottom of the climb really fresh," Vink said.
"It's a sedate stage until you hit the bottom of the climb, but I knew that the legs were good."
Vink has been one of the top riders on the New Zealand cycling scene for a decade, including finishing third overall and leading under 23 rider in the 2012 Southland tour, and runner-up for the past two years.
A seven-strong breakaway led by under-23 Australian rider Jensen Plowright (Aardvark Excavators) took the tour through northern Southland and around picturesque Lake Wakatipu, edging out to a lead of nearly 4min.
Plowright eventually took on the Coronet Peak climb alone, before being joined by Vink, Hamish Bond, Sam Gaze and Lionel Mawditt.
Vink bossed the climb to finish well over 1min ahead of Commonwealth Games gold medallist mountain biker Gaze. Bond was third.
A niggly crash in the shadow of the climb threw a scare into the peloton, and then defending champion James Piccoli crashed heavily at the hard right-hand corner leading into the climb.
He eventually recovered his bike and tried to mount a brave last-ditch assault, but it is likely the popular Canadian's title defence is over.
Overnight leader Matt Zenovich managed to limit his losses on the climb, but still slipped to 12th place overall.
Southlander Corbin Strong impressed on the hill, the world junior team pursuit champion finishing sixth overall.
Vink (WPC South-Joyride Apparel) has put himself in position to win the Southland tour before, but has missed crucial breaks at crucial times.
This year he believes he has the team around him to cling on to a yellow jersey which has proved slippery in the past.
He has a 1min 20sec lead over team-mate Oliver Martin, Gaze is third at 1min 21sec and Bond fourth at 1min 34sec.
"It's always good to have a lead, but things can change so quickly, so we have to be on our game if we want to hold it. I've been in this position before so I know what to do and we'll be ready for it."
In Vink's favour is the fact he has won today's stage from Invercargill to Bluff Hill before and he can draw on the experience of 2015 tour winner Brad Evans in the team van beside him.
"It's really nice having Brad as road captain. In other years I've been GC rider and captain, which is a hard thing to juggle."