Martin Crowe is such a legendary figure in New Zealand cricket - and New Zealand sport - that there is an ongoing crowd-funding campaign to buy the bat with which he scored his final Test century: 115 against England at Old Trafford in 1994. His cousin, Russell Crowe, is putting the bat, and various other pieces of Crowe's artifacts, up for sale.

That century by Crowe in Manchester was his 17th, and has stood as the figure chased by other New Zealand batsmen for more than 20 years. It had been caught up to by two players, and now Kane Williamson is at the top - alone, for now, having pipped Ross Taylor.

Off his 196th ball against England at Eden Park, the afternoon after that heady session when the visitors were skittled for 58, Williamson dabbed the ball towards gully, where it was parried away, and jogged through for the single. The celebration was characteristically understated, the job not yet finished. On this occasion, though, he could not carry on much further, pinned lbw by James Anderson with the new ball shortly after a rain break. But there will have to be a lot of rain, or an extraordinary reversal, for it not to be a century in a famous New Zealand victory.

It had long been assumed that the record would eventually go to Williamson. He scored a century on debut against India in 2010, and a superb unbeaten 102 against South Africa in Wellington as his second ton, though after 25 Tests he averaged 31.47 with three hundreds. It has been a four--and-a-half-year surge to the line.

The mantle of New Zealand's greatest-ever batsman could go with it as well, although that can be a lively argument as Chris Rattue put forth earlier this season. "Williamson - average 50 - can be nigh on faultless, the quiet assassin while a sport dies quietly. Williamson can leave you cold, even when he's hot," Rattue wrote in the New Zealand Herald. "Williamson pushes the score along, whereas Crowe lifted cricket up."

It's a fascinating debate, on a cricket level involving style, strength of opposition and conditions, just for starters. Shortly after the landmark had been brought up, former captain Stephen Fleming anointed Williamson New Zealand's greatest.

It has taken Williamson 64 matches to score those 18 centuries: that is one every 3.5 games, an outstanding conversation rate, and he comfortably has the highest average of any New Zealander to play a substantial number of Tests. He is 27 years old. Only New Zealand's shrinking number of Tests will stop him scoring a colossal number of hundreds.

But it has been a close race with Taylor, and, perhaps, the perfect story would have had him being the first to 18 centuries, given the close bond between him and Crowe. Taylor was visibly emotional when he equalled Crowe's mark against West Indies in Hamilton. Taylor actually had five centuries by the time Williamson made his debut in 2010, before a prolific run in 2014 propelled Williamson towards double figures, and it has been almost level-pegging since.

When it came, the record-breaking century was as beautifully crafted as many of the 17 before it. In sharp contrast to England's top order, Williamson's footwork was positive, he defended the ball under his eyes, and he left well. On the first afternoon, as England were still trying to digest their batting collapse, there was a statement of intent from Williamson when he twice lofted Moeen Ali down the ground in his first over.

He did have one significant moment of fortune. When Williamson had 64, Taylor struck a firm drive back towards Chris Woakes, who appeared to get a fingertip on the ball before it crashed into the non-striker's stumps with Williamson well short. Woakes appealed, but then indicated that he wasn't entirely sure. It went upstairs, and after much rock-and-rolling, Marais Erasmus said not out. That moment crystallised the feeling that this was going to be the innings for Williamson.

For a while, it appeared that he could do it on the first evening, which would have capped a day when everything went his way. But he played cautiously to see out the night session, not hitting a boundary off the last 56 deliveries he faced. No matter.

On Friday afternoon, he tuned up with a few throwdowns on the outfield, a process he will have been through on countless occasions before, re-marking his guard to face Woakes. He is a batting obsessive. If, one day, you can't find Williamson, he will probably be having a net. The rewards are milestones like this one.

Andrew McGlashan is a deputy editor at ESPNcricinfo