To paraphrase Monty Python, apart from 6453 runs in 101 matches, a highest score of 302 and a world-record 54-ball century in his final appearance, what has Brendon McCullum ever done for Test cricket?

Well, if those numbers alone don't impress you, how about his defining role, in the winter of 2014-15, in creating the team identity that, six years later, would result in little New Zealand becoming the inaugural World Test Champions, even while reaching three out of the last four World Cup finals across six years and two white-ball formats?

Or what about the fact that, to all intents and purposes, he has already revitalised English cricket once before? Had it not been for the lessons he imparted in 2015 on his great friend and then-rival Eoin Morgan, first on the field in an extraordinary World Cup humiliation at Wellington, and thereafter in passing on the Kiwi philosophy that Morgan's white-ball team would adopt as their own, there's no way they'd have reached the 50-over World Cup final four years later, let alone swiped the trophy from their former mentors too.

McCullum's appointment as England's new Test coach may look, on the face of it, to be a transcription error: the white-ball role would seem to be a far more natural fit. But in actual fact, it could prove to be a masterstroke, a chance to address head-on the listlessness that has defined England's Test endeavours in precisely the same timeframe as New Zealand's standards have soared. And at the very least - and in the words of Martin and Jeff's not-quite namesake, Sheryl Crow - it could end up being My Favourite Mistake. Anyone else up for dying wondering? Thought not.

Sure, the appointment will be greeted with horror by those who fear for the sanctity of the five-day game, and who are aghast at the notion of granting extra licence to an already slap-happy generation of batters - men such as Zak Crawley, whose inability to temper his attacking mindset has left that epic 267 against Pakistan looking like an outlier in his career record, rather than an expression of his generational talent.

But if one thing is abundantly clear from the horrors of the winter just gone, it is that playing safe with this appointment would have been a far greater sin than taking an educated punt on a man who has never coached a red-ball team in his life.

Over and above the need for a tactical genius or a ball-busting taskmaster, England's Test team is crying out for an identity. In a captain-coach axis of Ben Stokes and McCullum - two men who could easily have been All Blacks had their New Zealand heritage panned out differently, who in differing ways have been obliged to rehabilitate their public image, and whose similarities even extend to their maxed-out tattooed torsos - it's about to get slapped around the chops with personality.

Not that McCullum will necessarily prove as gung-ho in his stewardship as his reputation might suggest. "People might not believe this, but most of my preparation for batting is geared around defence," he told The Cricket Monthly in 2015. "If I can rely on my defence - defend straight and leave well - then the rest of my game flows from there."

That philosophy will be music to his new captain's ears - there are few straighter blades in world cricket than Stokes' at the outset of a Test innings. And McCullum will know too that good things come to those who wait, in more ways than one. On his first day as Test captain, at Newlands in January 2013, New Zealand were routed for 45 inside 20 overs - and that after the ugly sacking of his predecessor Ross Taylor, a situation that put a strain on their friendship and rendered the New Zealand team as unpopular as at any time in its history.

That was New Zealand's point of no return - the same point that England encountered at Melbourne five months ago, when they surrendered the Ashes with their 68 all out. Two years later, and after many honest conversations - including the soul-searching that followed the death of Phil Hughes in November 2014 - McCullum's men were the darlings of their nation as they sashayed through the home leg of their World Cup with a beaming grin and an assassin's creed. Even a thumping loss to the Aussies in the final couldn't detract from the huge gains made.

It remains to be seen whether England's Test fortunes can follow a similarly redemptive arc. But either way, McCullum's appointment is an extraordinarily exciting prospect for a format that can still, just about, lay claim to being cricket's "pinnacle", but needs the continued endorsement of the game's biggest names if it is not to collapse under the weight of its own self-importance.

Stokes, who pulled out of the IPL even before his appointment as Test captain, has been beating that drum with increasing urgency since the Ashes. He has repeatedly stated that Test cricket is his "No. 1 priority" and judging by his ballistic display for Durham at New Road last Friday, he's in quite the mood to back his words with deeds.

McCullum's resignation as Kolkata Knight Riders' head coach is quite the symbolic step too - an expression of faith in an ancient format from the man, lest we forget, whose opening-night century for KKR in Bangalore 14 years ago was the innings that sent the IPL stratospheric in the first place.

Not that this appointment should be painted as a Test versus T20 tussle. Quite the contrary, in fact: the worst mistake that cricket's traditionalists (for want of a better word) can make is to forget quite how malleable the longest format can be, and quite how much and how often it has already evolved in its 145-year history.

Ricky Ponting, Delhi Capitals' coach and another man who featured on Rob Key's long-list, was integral to the great Australia Test team of the early 2000s - a side whose brilliance owed so much to the fusion of skills that it absorbed from its hegemony in one-day cricket. Rattling along at four an over, with Matthew Hayden's pinch-hitting approach at the top of the order offset by Adam Gilchrist's death-hitting brilliance, and with Brett Lee and Glenn McGrath a contrasting pair of spearheads in each format, it set in motion a truly great era of Test cricket.

The same can still hold true now. No-one who witnessed Stokes' shot selection at Headingley in 2019, or Rishabh Pant's berserk onslaughts in Ahmedabad or Cape Town could possibly claim that T20 per se has been detrimental to Test cricket's overall standards. The trouble lies in its growing influence at the expense of all other formats. As Kevin Pietersen tweeted last week, even while missing the wider point that he was making about elite-level competition: "Every sportsman is a brand! All of you would work for less if you got paid way more for it! ALL OF YOU!"

And therefore, Test cricket has a choice. Does it do much as England has done in recent campaigns, and corral itself off from the zeitgeist - picking from a range of barnacles, workhorses and as-yet untainted rookies, none of whom have yet put themselves forward for an IPL auction and most of whom are never likely to anyway? Or does it seek to be bold - and address T20's dominance head-on by presenting itself as the means by which the very best can test the outer limits of their capabilities? Earn your living on the T20 circuit by all means, but step this way if you seek true greatness.

That's the option that McCullum's arrival would seem to place back on the table. Even though England are officially splitting their Test and white-ball coaching roles - and rightly so given the insane workload that his predecessor Chris Silverwood was obliged to take on - this is actually an appointment that can unify the two teams' philosophies.

Apart from anything else, it makes a virtue of the fact that Morgan, the white-ball captain, is basically untouchable as English cricket's grandmaster.

McCullum was master of ceremonies at Morgan's wedding, shares the same interests in horses and gambling, and last season they were the captain-coach alliance that propelled KKR to the IPL final. Irrespective of the differences between red- and white-ball cricket, you'd back them to craft a message that can be carried seamlessly from one format to the other, without the sort of compromises that Trevor Bayliss in particular was obliged to make in his approach to Test cricket.

It's fitting, too, that the first big Test (with a capital T) of McCullum's methods will come at Lord's against New Zealand next month. Everything that has been good about English cricket in the past decade seems to have had to pass this particular stress test - mostly notably the World Cup final in 2019, of course, but more pertinently in this case, the 2015 New Zealand Test in which England fleetingly showed a glimpse of what might have been had their white-ball prerogatives not got in the way.

That was the match that had it all. England collapsed to 30 for 4 and won; New Zealand racked up 403 for 3 and lost, and central to the renaissance was the then-young alliance of Stokes and Joe Root. Only months earlier, Stokes had been omitted from England's World Cup squad. Now he proved the folly of that decision with the fastest century ever seen at Lord's, as well as - in New Zealand's final-day chase - the first-ball dismissal of none other than McCullum, who had held himself back after the loss of three early wickets in the hope of instigating a "second launch" in their pursuit of a lofty 345.

"There's an element of pride that we continue to play a style of cricket that gives us our greatest chance," McCullum said after that match. "There will be times when teams can stand up to you and withstand the pressure and come out on top. You just have to doff the cap, say 'well played' and make sure next time you get the chance you go hard again and ask the same question."

It's hard to imagine that an England team led by Stokes, with Root still in the form of his life, with Jonny Bairstow back to a red-ball focus, and maybe even with Jos Buttler reimbued with a sense of purpose after his miserable Ashes tour will need much persuasion to buy into that sort of a vision from McCullum.

Buttler, in particular, is a fascinating case study. He was so clearly out of sorts in Australia - visibly overwhelmed at times by the limitless scope of Test cricket's possibilities. And yet somehow he was able to park those negative vibes come the start of the IPL, and tap straight back into the domineering mindset with which he had romped through the group stages of the preceding T20 World Cup.

A McCullum-Stokes Test team would surely wish to have Buttler as a central plank, but on his terms this time, with licence to play his natural game with a depth of batting options around him. That was the case in England's short-lived experiment with "total cricket" in 2018, in fact, when the side was loaded with allrounders down to No. 10, so that the team's big hitters had licence to trust their instincts, and the bowling had enough depth and variety to make every spell seem like an event.

There's no reason why, say, Alex Lees or Dom Sibley could not form a key part of such a rebooted England Test team - much as Alastair Cook's unhurried excellence was crucial to that 2015 Lord's Test - but it would have been on the terms dictated by the overall team philosophy, and not simply because they are likely to sell their wickets for a higher price than most.

After all, the game has evolved dramatically since Test cricket was last the overriding priority for England. At the recent Under-19 World Cup, the generation that grew up watching Morgan's white-ball revolution marched into the final with an array of drives, sweeps and ramps that might have been grafted directly from the men they had been idolising from the age of 13.

It won't be long before the likes of Jacob Bethell, Tom Prest and George Bell are pushing for Test recognition, and there won't be much point in forcing the white-ball genie back into the bottle when they get there. And frankly, why would you want to? As McCullum knows only too well, having reframed New Zealand as a team it needed to be, and not simply a less convincing version of Australia, if you're not true to yourself, you're lying to everyone.

England, in spite of the constant angst, have been white-ball trend-setters for the best part of a decade now. This appointment could be the first step towards fully embracing the implications. --Cricinfo