But Harbour's response showed they were up for this match - and where their danger lay.
They may have been bottom of the Championship going into this match but there has never been any doubt about their attacking potential. They demonstrated that with some forward raiding, a forceful run by first five-eighths Ben Botica - having perhaps his best game yet for Harbour - and a clever offload in the tackle by fullback Willie Walker for James Parsons to score.
They followed that a few minutes later with a brilliant solo 22-22 burst from sevens star and winger David Raikuna. He made Robinson look weak on the tackle with one shimmy, did Kade Poki with another and he found mobile lock Irwin Finau with the scoring pass.
With Botica banging them over from everywhere and Harbour's ball handling for once secure, they put the shield holders under real pressure, even with the rain intervening and the wind at their backs. Their defence was good enough to jolt the ball from hand in several Southland attacks. The key moment of the first half perhaps kept Southland in the game, just before the half hour. Harbour had mounted a multi-phase, patient attack and looked set to score and, at 17-7, that would likely have been a clear sign that the shield was heading to one of its northernmost destinations.
Southland are a fine set piece side, defensively lion-hearted and competitive at the breakdown - but not quite so adept at chasing down a big lead.
The Southland defence held, just, and when halfback Chris Smylie - another to have a fine game otherwise - knocked on, it felt as though Harbour might have shot their bolt. Botica - running, tackling and kicking so well that he announced his candidacy for Super rugby, at least - then pumped over another 50m-plus penalty for a 20-7 halftime lead.
Southland have great heart and are no mugs at running the ball (Cornforth could have had a second had he gone himself rather than try to find a support runner) and they were always going to mount an assault in the second half with the wind behind them.
They began to blow the Harbour forwards out of the breakdowns and it took only five minutes before halfback Scott Cowan scored unchallenged after a typical forward driving effort near the line.
With less than half an hour to go and the score 20-12, the rain came down in biblical proportions - but Harbour could have clinched it if second five-eighth Brendon Watt had been able to hang on to a clever Botica grubber under try-saving pressure from Cowan.
They gained some solace with another Botica penalty - the son of Frano kicked faultlessly - before James Wilson returned the favour for Southland. At 23-15, the game was in the balance, especially with Harbour beginning to make their trademark turnovers with the wet ball.
A Wilson penalty was reward for the pressure with 9 minutes to go.
Harbour began to wind the clock down with the forwards keeping the ball in hand but crucial territory was lost when replacement halfback Brenton Helleur scuttled down the blindside touchline. He had to kick ahead, to put Southland under pressure but, perhaps playing to team orders, he held on and then lost the ball.
Southland swept downfield, mounted wave after wave of driving attacks at the Harbour line and, just as it seemed the northerners would hang on, replacement hooker Jason Rutledge drove for the line and Cowan slipped through like an eel to clinch the game.
Cowan - scored two, saved one - was Southland's hero along with ball-poaching flanker Hardie. For Harbour, Botica, Mat Luamanu, Finau, Smylie, their lineout and the highly dependable and elusive Walker were splendid - and must wonder how it is that they don't have the shield.
In the end, Helleur wasn't alone. Harbour made too many mistakes in the second half instead of playing field position, sewing it up tight and waiting for the penalty. They did so much right, enough to have lifted the Log.
Which is what makes the shield - still - so great when it comes to drama and the devastation of putting even a simple foot wrong with everything on the line.
Southland 25 (T.Cornforth, S. Cowan 2 tries; J. Wilson 2 cons, 2 pens)
North Harbour 23 (J.Parsons, I. Finau tries; B. Botica 2 cons, 3 pens).
Halftime 7-20