Root's innings, the 14th time he has gone past 150 in Tests, has now put his average back above 50. It allowed England to declare on 435 for 8 and have two cracks at the New Zealand batting order before and after lunch. The hosts were reduced to 138 for 7 before the rain came to wash out the final two hours of play, for the second day in succession.

"I felt like I owed that to the group," Root said. "It's been a while since I made a solid contribution. To be part of such a big partnership was really pleasing and I think the best thing was I had the best seat in the house to watch Harry go about his business. It's a joy to watch him play at the minute. He certainly made my life a lot easier out there, the way he manages to wrestle momentum in our favour and constantly put bowlers under pressure.

"When he comes and plays as he does - if you slightly over-pitch he hits you over your head, if you miss short he goes midwicket, he'll back away and hit you through the off side - it's difficult to know where to bowl with him. When you get down the other end it just feels like there's less pressure on you, and more opportunity to get him back on strike and down the business end.

"I felt we had a really good understanding, we negated a few modes of dismissal by getting down the crease. We fed off each quite nicely and made it difficult for them to bowl one length for us."

"I think it was a brilliant call from Ben," Root said. "It felt like that 40 minutes before the break, the sun was out and with 40 minutes of sun, a heavy roller and 40 minutes of sun at lunch, it might have changed the wicket.

"It didn't work out like that, it gave a better opportunity to make the most of conditions. The way we're playing at the minute with the confidence we've got, seeing the ball move around with the No. 1 Test bowler, the two leading wicket-takers we've ever had, it just seemed a very brave and attacking option. Full credit to Ben, as you'd expect, for taking it on.

"He's just walked so naturally into the role, he's managing the game really well and everyone is responding to it. I just think was a brilliant call from him, it would have been very easy for us to keep going and we might not be sat here with them seven-down tonight. Credit to him, he's doing a great job."

As for the match going forward, a follow-on could be on the cards, given the likelihood of more rain interruptions and the relatively light workload of England's bowlers so far. Either way, the result will decide whether this century ranks as one of Root's best since the start of last summer.

"Potentially," he answered when asked whether this one was top of the four, the others having come in the opening matches of last summer, including two successful run-chases at Lord's and Edgbaston. "We'll see how the game turns out. You always judge how well you've played off the back of a result and I'm certainly sat here in this position, at the end of day two, having them seven-down with a huge lead is very satisfying right now. Hopefully we can follow through on it and continue all the good cricket we've played up to now."