'Pretty surreal,' says NZ quickie Henry after destroying Proteas

New Zealand quickie Matt Henry was over the moon after his bowling heroics humiliated South Africa in Christchurch on Thursday.

The Black Caps dominated the Proteas to hold a 21-run lead on day one of the first Test after Henry spearheaded the attack with a career-best 7/23.

Henry's bounce and movement saw South Africa fold for 95 before tea, and at stumps New Zealand had benefitted from the wicket browning off in the late afternoon and were 116/3.

Henry Nicholls was not out on 37 with nightwatchman Neil Wagner, dropped in the final over, on two.

"Obviously today's been a great day for us," Henry said, describing his own performance as "pretty surreal" returning the third best bowling figures for New Zealand behind Richard Hadlee and Ajaz Patel.

Henry's previous best was twice taking four for 93, and he has struggled to be a regular member of the New Zealand attack, where Tim Southee and Trent Boult have long been the new-ball bowlers.

It's only his 16th Test in seven years but with Boult on paternity leave, the Christchurch-born Henry relished the chance to perform in front of his home crowd.

"It's not always easy," he said of the long gaps between Tests.

"You try not to focus too much on those external things you cannot control and make sure I'm still in that mindset of trying to get better every time you get that opportunity to play for New Zealand."

Crucial to New Zealand's performance was Tom Latham winning the toss - for the first time in the nine Tests he has been captain - and putting South Africa in to bat.

The Hagley Oval, with its green-tinged wicket, was tailor-made for New Zealand's swing and seam attack and Tim Southee set the standard with the opening ball, a huge inswinger to Dean Elgar that finished down leg side.