OPINION
It's perhaps too simplistic to say Brendon McCullum has single-handedly revived the fortunes of English test cricket, but it's hard to draw any other conclusion.
Three tests, three wins, and the transformation of a shambolic team with next to no confidence and a dreadful recent record into one which played with conviction, courage and a cavalier spirit which was far too much for New Zealand to deal with.
This is largely the same group of players that endured such a wretched time in the last two years, now playing like world-beaters. One swallow doesn't make a summer, but as entrances go, it's difficult to remember a similarly instantaneous impact.
If Jonny Bairstow had got out recklessly and early in any of his swashbuckling, match-changing knocks, or Joe Root had come to grief reverse-ramping Neil Wagner, you get the feeling McCullum would simply have shrugged his shoulders, smiled wryly, and congratulated them on having a crack.
In basic terms, that's clearly his mantra. Bairstow's first three innings of the series were one, 16 and eight. Those sorts of scores might have sent pre-Baz Jonny into his shell. Instead, he then hit 136, 162 and an unbeaten 71 with those 369 runs coming off 293 balls. This is test cricket, remember.
On the face of it, McCullum isn't a particularly analytical coach. Throughout this series, I never once saw him poring over a laptop, or even taking any notes. There he sat on the balcony, ball after ball, over after over, day after ever-more successful day, just watching it unfold through his ever-present sunglasses, England cap pulled down tight.
McCullum hasn't changed this team by crunching numbers or examining and refining techniques. He knew he had the raw materials and has basically just given the players permission to enjoy their cricket again.
I once heard him talk about T20 run-chases. Scoring 180 off 80 balls may seem like a very challenging task, but, he said, you only have to hit 20 of those balls for six and you're actually chasing 60 off 60. That's a very McCullum-esque approach, but the point is he feels targets are there to be overhauled, not politely, yet firmly declined as they so often are in test cricket.
England chased down 296 at Headingley, 299 at Trent Bridge and 277 at Lord's. A year ago, they would have turned their noses up at chases of that magnitude. Now they're getting there with whole sessions to spare.
McCullum is a self-confessed test cricket enthusiast. At a time where the game is in a fight for its relevance, he wants it to not only survive, but thrive. He and his freshly invigorated England are certainly doing their bit.