Boult had bowled 10 overs for no wicket on the opening day of the Boxing Day Test in Christchurch, with half of those maidens. In fact, through the tour of UAE before coming into this series as well, he hadn't found too many wickets, even when he was bowling well. In the first Test in Wellington, where Tim Southee picked up six wickets in the first innings, he finished with just two scalps for the match.

"I suppose it can be easy to get frustrated a little bit, figuring out why things aren't happening," he told the press on Thursday, 27 December, after finishing with 6/30, explaining how he hadn't let it get to him. "With a little bit more experience – I'm getting old now – realising it can be funny game, it's probably about turning up with the right attitude, trying to put the ball in the right areas, and I was just lucky enough to get a bit of reward."

The Sri Lankan tail had little answer to the late movement Boult got. Their mix of right and left-handers meant the bowler got shape both ways. The last four wickets were all lbw, with a couple of the batsmen not offering a shot.

"It's all about rhythm for me," he said. "It's about getting into a groove. A couple of wickets gives you a bit of confidence and just lets you go about your thing.

"The plans were simple this morning – it was about building pressure on the guys and it was nice to exploit a bit of their weaknesses with some swing bowling. I was just trying to pitch the ball up really."

On the first day, it was Southee who added three wickets to his kitty to take his series tally to 11. On Thursday, even though Boult didn't leave him any wickets to get, he played a big role, keeping things quiet at one end, while also doing a fantastic job with his catching at slip.

"One of the strengths of the side, of the bowling unit itself, is bowling for each other and sticking to that plan and being willing to hang in there and be patient," said Boult. "Timmy got the rewards last week and I'm sure there's just rewards for the other guys around the corner as well.

"I think that's one of the main reasons we are so successful is bowling from both ends and bowling in those partnerships. That's probably what we'll look to do later in the game."

New Zealand are in a strong position in the Test, extending their lead to 305 with eight wickets still in hand.