Although Australia, trailing 22-3 at the interval, hit back with two tries in the second half, the All Blacks were always comfortably in charge. In comparison, New Zealand managed only one try but Mehrtens quickly booted them into an unassailable lead and was successful with all 10 of his kicks, one conversion and a world record-equalling nine penalties.
Asked if he was worried about Australia scoring two tries to one, the All Black coach, John Hart, said: "The 34-15 scoreline looked pretty good to me. That was a very good win. We knew we had to start well and stop the momentum of Australia, and we did. It was a very satisfying night at the office."
He also praised his captain, Taine Randell, for playing "his best match for the All Blacks".
The Australian coach, Rod Macqueen, admitted New Zealand were the better side. "The All Blacks started so well and we started slowly. We were under tremendous pressure and made a lot of simple errors," he said. "That will have to improve if we are to do any good in the Bledisloe Cup [against New Zealand] and the Tri-Nations, but the World Cup is our ultimate goal."
Australia, who went into the game on the back of a 10-match unbeaten run, were woeful in the first half and gifted New Zealand their ninth- minute try when the winger Joe Roff fumbled the ball on his own line and the scrum-half Justin Marshall pounced to score. Mehrtens, who had already opened the scoring with a penalty, duly added the conversion and then kicked another penalty three minutes later. That put the All Blacks 13- 0 ahead with only 15 minutes gone and their outside-half added three more penalties before the interval with just one successful penalty kick by Matthew Burke in response.
A storming run from the All Black hooker Anton Oliver two minutes after the interval led to another Wallaby infringement, allowing Mehrtens to extend the lead to 25-3. He made it eight from eight five minutes later.
The Australians' first real chance came in the 51st minute but Christian Cullen's copybook ankle-high tackle stopped the centre Daniel Herbert crossing under the posts. But Australia were not to be denied and George Gregan scored by beating the opposing No 9 Marshall behind the line to a loose ball from a scrum. Burke missed the conversion.
Mehrtens slotted his eighth penalty after the Wallaby prop Glann Panoho used his elbow in a ruck. In contrast, Burke was kicking for touch or Gregan was using tap penalties in the hope of setting up a try instead of going for goal. So far behind were they that this was really the only choice for Australia and it finally paid off after 69 minutes when a slick backline move put Herbert over for a try under the posts which Burke converted to make it 31-15.
It was left to Mehrtens to have the final say with his 10th successful kick.
New Zealand: Wilson; Cullen, Ieremia, Gibson, Umaga (Lomu, 65); Mehrtens (Brown, 71), Marshall; Hoeft (Feek, 58), Oliver, Meeuws, Maxwell, Brooke (Willis, 69), Mika (Blowers, 75), Kronfeld, Randell (capt).
Australia: Burke; Tune, Herbert, Grey, Roff; Horan, Gregan; Panoho (Crowley, 59), Paul, Noriega, Giffin, Welborn (Connors, 59),Cockbain, Wilson, Strauss (Kefu, 46).
Referee: D Bevan (Wales).