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Williamson crafted an excellent 89 as the Black Caps took control of the first test against India, reaching stumps on day two at 216-5, with a 51-run lead after they had rolled the visitors for 165 before lunch.
After their dreadful displays in Australia, the Black Caps are back where they play their best cricket, and are threatening to take down the world No 1 test side, who have won seven tests on the trot.
It's no sure thing yet – late wickets boosted India's cause, and many a test at the Basin Reserve has been flipped by the batting-friendly third innings - but Williamson has ensured India will likely begin that innings significantly in arrears, assuming the remaining Black Caps batsmen can play their part.
There's a chance this could be Williamson's biggest contribution to the series, in part due to a finger injury suffered on the first ball he faced, when Ishant Sharma rapped him on the glove. Bandaging was required with Williamson in some discomfort, and whether he can field, or has done lasting damage to his digit, will be determined with a precautionary scan overnight.
However, he may have already done the most damage to the Indian bowling attack, producing a superb and timely knock, following a comparatively lean run in tests. The Black Caps skipper had struggled in Australia and Sri Lanka, and had Joe Denly not committed one of the worst drops in the history of cricket when Williamson was on 62 against England in Hamilton, Williamson would have been averaging just 19.8 in his last 10 innings.
Yet, Williamson always talks about the importance of adapting to conditions, and in New Zealand conditions, he makes the bowlers adapt to him.
Once over the initial pain, Williamson showed that none of his typically classical shots were to be restricted by his finger injury, with the back-foot punch in especially delightful use to dispatch anything short behind point.
He also had a superb platform from which to play those shots. Resuming at 122-5, India's middle order offered no resistance, with the last recognised partnership of Ajinkya Rahane and Rishabh Pant ending with a disastrous runout, before Tim Southee cleaned up Ravichandran Ashwin the following ball with an exquisite outswinger.
Southee, who ended with 4-49, cleaned up the tail alongside day one standout Kyle Jamieson (4-39) as the Black Caps bowlers put in a better performance than their fancied Indian counterparts.
Sharma was the most potent, taking the first three wickets to fall. He removed Tom Latham - strangled down the leg side for 11 - and Tom Blundell, who failed to flatter before being bowled between bat and pad for 30.
Williamson received support from Ross Taylor, who earned a standing ovation as he walked out to the crease for his 100th test. He produced a trademark slog sweep six off Ashwin, and smacked seven boundaries in his stay, but on 44 Sharma saw the back of him too, with the extra bounce on offer seeing Taylor lob a delivery off the glove to a grateful short leg.
There were few chances coming from the bat of Williamson. Lacing boundaries through the offside, his timing was excellent and his drives picturesque, and he showed some nifty footwork as well to dance down the track to Ashwin and bring up his fifty through mid-wicket.
The controlled innings made it seem a century was on the cards, but on 89, a rare loose shot was snaffled up at cover, and when Henry Nicholls departed for 17 before stumps, India had found a path back into the test.
But make no mistake, the day still went to Williamson, and New Zealand.