Despite its grand pretensions, international cricket is a pretty small world, and perhaps no-one could understand this better than a son of Dunedin - the sort of one-horse (and several albatross) town where everyone knows everyone, and nobody's business stays their own for long.

"It'll be difficult, no doubt, looking across to the New Zealand balcony at times - but that's just life," McCullum said. "I'm very proud of my heritage, very proud of my upbringing and what I've been able to achieve for my country. But this is a job where you're being tasked with trying to bring about change, and hopefully do something which lasts a long period of time into the future, and that's a pretty enticing opportunity."

By his estimation, it's a pretty urgent opportunity too. Even after a decade of T20's full-swing revolution, not many of the game's grandees are willing to admit - as McCullum readily does, despite the nature of his new role - that Test cricket is "not as popular as what it once was".

But, again, perhaps it takes a Kiwi to speak such plain truths - particularly one as authoritative as McCullum, the owner of 101 hard-won Test caps, and the acknowledged Godfather of the reigning World Test Champions. For just as global warming is more urgently recognised by those countries dealing with rising sea-levels and creeping desertification, so it is New Zealand who can more readily sense the tide going out on the format.

Even as they sit at Test cricket's summit, cherishing their first global trophy, New Zealand know they remain at the mercy of, as it were, cricket's more developed economies. India and Australia may still be meeting their commitments, and have produced some of the best Test cricket of the decade in the past 12 months, but England - with one win in 17, including a supine Ashes defeat in the winter just gone - most certainly are not. And, as McCullum recognises, their failure to nurture the format's environment endangers the game as a whole.

"If Test cricket is going to survive and thrive, then England has to be at the top of the tree," McCullum said. "If the Ashes isn't competitive or if England aren't vying for No. 1 positions, then Test cricket is in trouble, because of the support that the people of England and the UK have for Test cricket. No one else really has the same affection or has the ability to make the game sustainable, I think, so that's one of the challenges."

Even before a ball has been bowled in the McCullum era, it feels as though all the mystique has been stripped away from his role. He may be England's fourth overseas Test coach out of six this century, but Duncan Fletcher he is not. There's nothing inscrutable about his methods, no sense that he'll spend six weeks lurking in the corner of the dressing room, sizing up the characters at his disposal before opening his mouth for the first time, which was the experience that Darren Gough recalled when Fletcher joined the set-up in the autumn of 1999.

"My skills are around taking a team from a bit of trouble into a team that has long-term sustainable success. That is what I believe," he said. "You are not always going to achieve it … I might be terrible! I might change all things completely. We'll see how we go. But if you are going to change your entire life for something, it has got to be a pretty big challenge." And you can't say fairer than that.

"Yes, there's risk with it, but everyone that's been around English cricket talks about how good a player this guy is, and what his potential is," he said. "Let's see it. Give him the opportunity in a position which has been difficult. If he's able to nail it, then your middle order looks very, very good."

That general theme of tyre-pumping pervades McCullum's initial messaging. English cricket, he acknowledged, has a tendency to get more lugubrious than many, and while he believes that the pandemic's bubble lifestyle was a big factor in the Test team's recent collapse of resolve, the upshot is a squad of players "who are maybe just a little bit stuck by the fear of failure, rather than the possibility of success".

"My first job," he added, "is to bring a real fresh approach, and a relaxed style [that] simplifies things. It's not about finding someone who's got a better cover drive or a better hook shot, it's just allowing the guys to be able to make good decisions because they're in a clear frame of mind and a positive environment."

To that end, the McCullum era will surely be defined by the extent to which he can harness the one true English success story of the past decade - the pioneering progress of their white-ball set-up - and align the Test team to that same unfettered approach. Back in the early days of the T20 revolution, McCullum himself had been a prime example of how the very best Test players of his age could make a seamless transition to the shortest format. The challenge right now is to prove that that journey can be a two-way street, and that players who currently have eyes only for the T20 prize can be persuaded to give the grand old format the same go.

"A lot of people are now coming into the sport and they're looking purely at T20," he said. "Wouldn't be great if, in a couple of years' time, the next wave of youngsters coming through want to play Test cricket as the No.1 priority? Not just because the game is appealing, but the personalities that are involved are good role models and it looks like a fun game to play. That's kind of a fanciful idea, but unless you have that held up, then you won't be able to achieve it."

What that means for the make-up of the Test team going forward remains to be seen, but the clear implication is that McCullum will seek to sell his vision to some of England's key T20 personalities - most notably, perhaps, Jos Buttler, the current Orange Cap-holder at the IPL, whose disillusionment during the Ashes was at such stark contrast to his buccaneering short-format form.

"There's no reason why, if you're good at T20, you can't bring those skills into Test cricket," he said. "You look at some of the guys who have dominated the IPL in the last two months: if you're able to find that type of game they want to play at Test level, they are some of the best players in the world. So it's just a matter of trying to identify how they're going to do that.

"Everyone's got [that fear of failure] to a degree but it's probably just a little more English than others," McCullum added. "But one thing I can guarantee is that when you do get to that state where you're playing the game for the game's sake, because you enjoy it and you're invested in it, you immerse yourself in that moment.

"Cricket's a great game to play. It's not a great game when you're worried about all the other stuff which goes on. That'll be the message which I keep ramming home to the boys."

Whatever happens from hereon in, it's already clear that it's unlikely to be dull. And, with a fair wind, it could be transformative - not just for England, but for the well-being of Test cricket as a whole.