The smile that creased Martin Guptill's face was worth the price of admission, the monthly subscription fee or the rude interruption to your Sunday long lunch, or whatever price you want to put on it.

After slog-sweeping Australia's high-class leggie Adam Zampa he held the pose, as is his habit, but lifted his head in time to watch the ball sail onto the roof of the Cake Tin. It was a mighty hit, the third time he's achieved the feat.

They're the sort of shots you remember long after the matches are forgotten – and in reality a bilateral Twenty20 series decider between two old rivals is not going to feature in many future folk songs.

But it meant something more than it might have because the Black Caps, for all their achievements of late, have had a mental block when it comes to their trans-Tasman neighbours.

Not this time though, the seven-wicket thrashing achieved with a whopping 27 balls remaining was the perfect exclamation mark on a series affected but not ruined by lockdown. It also prevented the inevitable "choke" headlines after New Zealand let a 2-0 lead slip in the five-match series with some decidedly ordinary cricket.

There would have been demons in the dressing room following Friday night's ill-conceived chase. How could there not be? Same ground, same strip, same attack.

New Zealand needed to change things up a bit and did so, inserting Devon Conway at the top of the order to replace Tim Seifert, the most discombobulated of the home batsman this series.

Martin Guptill top-scored for the Black Caps. Photo / Photosport

While it might have been a horses-for-courses decision, it appeals as a more sustainable partnership in the long term. There's a the left-right element, which fielding captains never enjoy, plus it pairs Conway's consistency and ability square of the wicket with Guptill's mercurial power hitting straight down the ground.

Seifert, in turn, could benefit from the match dictating how he plays, rather than asking him to dictate the innings, a task that appeared to stifle rather than liberate his talent.

The move worked, with the 50-partnership coming in the sixth over, the 100 in the 12th. It featured some pleasant, heady stroke play from Conway (36 off 28) but more importantly an acute sense of what his role was at the various stages of the partnership.

Guptill, who looked like he might have aggravated a leg injury, rode his luck early but he will feel entitled to do that having suffered from an acute lack of that commodity for most of the summer.

Once he got a couple out of the screws there was nothing lucky about his batting, particularly in that Zampa over where his nudge onto the roof was one of three sixes.

They were separated at 106 but the strength of the start meant there were only minor tremors felt when skipper Kane Williamson was unlucky to be given out first ball. It didn't look like a great shout in real time but replays suggested the lacquer on the ball would have clipped the varnish of the wickets and created just enough friction for the bail to be released from its groove.

Guptill went next, top-edging on 71 (46 balls), with just 19 needed at about three an over. By that stage the ebullient Glenn Phillips was in his stride. He slaps as often as he strokes the ball but when he slaps he does so really hard.

One such shot nearly collected Riley Meredith in his follow through, while another ended the game with a six over long-on.

It was a comprehensive win set up by a much more disciplined and well-planned bowling effort.

This match started like many of the others: with Tim Southee rapping Aaron Finch on the pads and umpire Chris Gaffaney showing something close to contempt for the bowler's entreaties. It's already cost Southee a spot in the naughty corner this series and although the umpire got this one right his dismissive reaction to Southee's appeals are a curious study in body language.

Gaffaney did get to raise his finger two overs later when Trent Boult trapped Josh Philippe dead in front. Philippe (two) had swapped places with Matthew Wade in the order – the move only worked for one of them.

Wade is an interesting cricketer. He loves to play the archetypal Aussie hard man but looks much more effective when he's playing the ball not the man. His innings (44 off 29) was a delight, coming as it did off the back of a string of low scores. On a difficult wicket, everything seemed to find the middle, including the flick off his pads that carried to Guptill in the outfield when he seemed set to take Australia through to a big score.

He fell to Boult, who was a rare seam-up presence in the attack.

Williamson leant on a spin-heavy approach, with Mitchell Santner and Ish Sodhi complemented by Mark Chapman and Phillips, who had the misfortune to deliver one of the worst overs in professional cricket history.

Phillips is a versatile player. He can open, bat down the order, take the big gloves as a wicketkeeper or buzz around the outfield like a Labrador puppy let off a leash.

With a bit of luck, he won't be required to bowl his orthodox spin again. OK, that's too harsh, but his second over was the sort of thing you might expect to see at Saturday morning cricket, often followed by a slightly embarrassed parent comforting a tearful child on the boundary.

There were balls that barely landed on the mown strip and a waist-high full-bunger that was summarily dismissed.

Mind you, Phillips could be forgiven for feeling a little ripped off after Ish Sodhi started the 18th over with two horrendous full tosses that Marcus Stoinis and Ashton Agar plopped into the hands of Guptill.

That over was the 12th and final over of spin in the innings, a New Zealand record of such.

Australia's innings was muted. They reached the end of the 19th over in a similar position to Friday night seeking the same sort of 26-run explosion that Finch delivered off Jamieson.

With the tall right-armer dropped for this match it was instead up to Southee to stem the flow. It was… interesting. Two wides and a no-ball in the first four balls promised little but a classic yorker put paid to Mitchell Marsh's six dreams and Southee, and Australia finished on 142-8.

It was a gettable target.