Duffy, Ajaz rip through West Indies as New Zealand seal series 2-0

Did New Zealand take too long to declare? Had the pitch broken up enough to make batting in the fourth innings as hard as it was forecast? Was this Kane Williamson's final Test at home?

Doubt filled the air as an absorbing series eased into its final day and then dissipated in the wake of a West Indies collapse. Eight wickets fell for 25 runs after the morning drinks break with Jacob Duffy (5 for 42) taking over Sir Richard Hadlee's record for most wickets in a calendar year for the Black Caps - and bumping Trent Boult off the top spot for damage done over a single home series.

West Indies went from 87 for 0 to 112 for 8 to 138 all out with Shai Hope exemplifying their state of mind - out to a full toss without playing a shot on 3 off 78.

The Bay Oval is unique. It houses the only surface in New Zealand that is better to bat at the start and turns increasingly treacherous. The wear and tear was so profound that instead of a single solid block, it turned into a mess of broken plates, wobbling about under the light roller or even simple touch. It fascinated everyone, including the home team's players. Daryl Mitchell was even moved to do that thing most people do to check and see if something is real - he pinched it and it was proven he wasn't dreaming.

So the spinner they brought in specifically for this Test match was offered centre stage. Ajaz Patel, so often peripheral to the team's needs at home, was generating 15.8 degrees of turn. That was part of why Hope thought he was safe against a ball delivered from well wide of the crease. Ordinarily it might have pitched harmlessly and spun away harmlessly but the cross wind caught hold of it - as Ajaz had intended, because all game he was looping it up at 70kph or so - and it careened into the right-hander's front toe.

It took an age for New Zealand to review. Only one second was left on the clock when Tom Latham was reminded that the ball hit Hope on the full, which means from the point of contact, the projection becomes a straight line. With Ajaz's angle from around the wicket and no shot offered, there was a chance lbw was on. Ball-tracking took another age to come up but when it did it showed three reds.

New Zealand had engineered that dismissal with smart field placements as well. They crowded Hope. Slip in. Two silly points in. Two short covers in. They had already seen him defend full tosses so were encouraged to bring their field up and make the batter worry that even a firmly hit defensive shot could end up going to hand. That's why Hope chose to leave. He thought he was being sensible. He didn't realise he'd been cornered. No idea why because New Zealand had made it explicit. "This is hallway cricket," they chirped as the walls closed in.

Brandon King made an enterprising half-century but from there West Indies' scorecard gave way to eight straight single-digit scores, including Roston Chase's 5 off 26. The captain ends the tour with 42 runs at an average of 7. He might not have been able to protect himself even if he had been in form because his wicket - caught fending at second slip - was the work of an accurate bowler generating vicious bounce off a length. Duffy was the perfect weapon for New Zealand. They'd wised up to him only in August and four months later here he is, with more than twice as many wickets as his nearest competitor in this series (23 vs 10).

And it wasn't just that he was bunging it into the pitch and waiting for it to misbehave. Alick Athanaze's wicket highlighted that Duffy has the smarts to lead this attack. He began by testing the West Indian's back foot play and bringing natural variation into play. There was plenty of up and down bounce to worry the batter. But that wasn't how he wanted him. Just where. Duffy had pinned Athanaze to his crease and having accomplished that, he snuck in the fuller delivery and nicked him off on the move.

Duffy and Ajaz bowled nearly 70% of New Zealand's overs in the final innings. The left-arm spinner went unchanged from the moment he was introduced into the attack on the fifth day (29-18-23-3). Together they were undeniable.

New Zealand took the series 2-0 and climbed to second place on the World Test Championship table. Later in the evening, they'll part ways with Williamson who has already said without saying that he won't be with them in January in India. "There's a pretty large block away from the group as well, and there'll be more conversations had," he announced on Sunday. On Monday, he celebrated a hard-earned Test win. On Thursday, he'll enjoy Christmas with his family. Beyond that, his future appears unknown. He might already have played his final Test match at his home ground.