Trent Boult was sitting on a cardboard box - presumably containing water bottles - all padded up and waiting for his turn to bat at the Basin Reserve nets. An elderly gentleman came by and asked him if he would like a chair, because that box did look rather low, but Boult cheerfully said he was all right.

Not long after that Boult's turn was up, but as he entered the gate, he paused for a moment at a whiteboard listing the net bowlers and their style of operating. He bent down, rubbed out the F from the RAF (presumably, right-arm fast) next to one of the names and sketched in an M (presumably for medium) to the amusement of those close enough to observe his act. The friendly sledge - it must have been - as he walked into the net was inaudible.

Those few minutes may not be indisputable proof of Boult's sunny disposition, but they did not contradict his Northern Districts coach James Pamment's assertion that he is a "humble young man" and "a pleasure to be around."

England, though, are unlikely to see that side of Boult during their World Cup match against New Zealand in Wellington on Friday, because Pamment also says Boult is a "fierce competitor" - be it fishing or playing golf - and "a very aggressive guy with the ball in his hand."

They have also had problems against left-arm quicks in the recent past. Their batsmen's failings against Mitchell Johnson across the Tasman sea have been meticulously documented, and even Mitchell Starc has troubled their top order in the recent tri-series. Boult swings the new ball later and to a greater degree than both the Mitchells, and England will have to watch for both deliveries, the one that bends in viciously late and the one that zips across, and spotting the movement is only half the challenge.

Brendon McCullum talks about a blueprint his team has been playing to in the lead-up to the World Cup - one that prescribes attacking cricket - and Pamment says Boult is the sort of bowler who complements the New Zealand captain's philosophy. Boult is at present one of New Zealand's best two quicks - the other is his good mate and sounding board Tim Southee - across formats and it's certainly not because they are short of options. It wasn't so not too long ago, though.

When India toured New Zealand in early 2014 and played five ODIs, Boult didn't get a game. New Zealand chose their specialist quicks from among Southee, Kyle Mills, Mitchell McClenaghan, Hamish Bennett, Adam Milne and Matt Henry. Boult was reserved largely for Test cricket.

"The sheer volume of cricket we were playing meant we weren't necessarily able to give him [Boult] the opportunity we would have liked to with the white ball," McCullum said. "Other guys were standing up and performing well. So that's probably why he didn't get a great deal of opportunities, but I think the way he's stepped up and performed the role for us so far - him and Southee are a very dangerous bowling partnership.

"His ability to swing the ball - and also the two new balls help too - he's really developing nicely as one of our strike weapons at the start. He'll face some challenges where opposition teams will try and be more aggressive against him, but I think he's got the skills to overcome that. He's a nice level-headed guy…so I'm confident he will be able to do a good job for us even if he is under a bit of pressure at times."

Boult won his place in the World Cup squad ahead of Henry and then his spot in the XI ahead of Mills and McClenaghan. It wouldn't have surprised Pamment.

"I've known Trent for a long number of years. We're from the same, small district, we're from the Bay of Plenty," Pamment said. "His desire and determination to be an outstanding bowler has always been evident. I guess the most significant thing about Trent is that he's very self-sufficient. He drives himself very diligently. He's a good learner and he's always been passionate to be one of the best in the world."

The goal of being among the best in the world seemed distant in 2009, when after a limited-overs tour of Australia during which he didn't play an international game, an 18-year old Boult had stress fracture of the back that sidelined him for about two years. His brother Jono Boult, who also plays for Northern Districts, said Trent had taken that experience on board. "I think that helped him to getting back to where he is now," Jono Boult says, "with the strength and conditioning sort of stuff."

Strength, conditioning and athleticism are words often spoken by Pamment when talking about Boult's growth as a bowler over the last few years. He says a tremendous improvement in the bowler's fitness has allowed him to exploit his greatest gift.

"He's got a lovely wrist position and the fact that the wrist goes right behind the ball gives him that control," Pamment says. "And as he's got stronger as an athlete, he's increased his pace and he's increased his accuracy through being stronger at the crease. He's always presented the ball fantastically well but as he's got stronger he's been able to hold himself at the crease and run in with more vigour. It just complements what has always been a great strength of his, which is that wrist position.

"He's a fantastic athlete now and I think he's still developing as an athlete as well. He's very diligent around his preparation with his strength and his conditioning. He's an outstanding athlete first and foremost and then his skills as a cricketer come to the fore."

Pamment also believes Boult can get far better, and given his penchant for self-improvement he could develop steadily over several years to come. "I think he's got a lot of development to do and he is passionate about doing it. He's probably enjoying the success that he has been experiencing but he will be working extremely hard to continue to develop, and most importantly to contribute to what is a good team at the moment. He's passionate about that, I don't think he's anywhere near his peak. He'll get fitter, he'll get stronger, and his knowledge around what is required to do the job especially in white-ball bowling will only develop with more experience."

Boult's burgeoning skills were recognised at the IPL auction three days into the World Cup, when a bidding spiral ended with him being bought by the Sunrisers Hyderabad franchise for $633,000. There have been concerns in the past of how young cricketers deal with the challenges of sudden fame and fortune. Boult seems well equipped.

"He's from a very good family, a very supportive family," Pamment says. "He's very humble, he loves his golf, he loves his surfing, and he's a pleasure to be with, you know. He's a nice young man. He's got a very good balance in his life."

Jono Boult also painted a similar portrait of his brother - that of a "normal sort of Kiwi young guy…into his golf and fishing and surfing. Just the same as other cricketers really, nothing too interesting there!"

Apart from the ability to swing the ball prodigiously and late, and accurately, at pace, as England might find out on Friday.

George Binoy is an assistant editor at ESPNcricinfo