McCullum's first series as head coach against NZ proved a huge success, with England banishing their long run of poor form and chalking up three thrilling victories at Lord's, Trent Bridge and Headingley.
Even more striking was the way they went about their business, scoring their runs at a staggering rate of 4.54 and chasing down supposedly challenging totals of 277, 299 and 296 with apparent ease.
It all adds up to a stunning calling card for McCullum and captain Ben Stokes, who promised entertaining cricket when they were thrown together at the start of the summer.
McCullum kept a low profile during the series but clearly felt his side had made a splash.
"The world Test champions were a formidable opponent to overcome and the alarm bells have probably gone off somewhat around world cricket as to how this team is going to play," he said.
"When Ben's out there captaining he's constantly making plays, which I think is great because it means at least we're in control, regardless of what the scoreboard says.
"Then when he's batting, he's pushing the envelope as well, which is sending a message to not just our dressing room but to other dressing rooms around the world that this is how we're going to play.
"Obviously you want to be the No.1 team in the world and you want to achieve the ultimate success, which is being world Test champions, winning the Ashes and beating the top teams consistently.
"That's the end goal, but what we need to do first of all is enjoy what we've been able to achieve over the last three weeks and understand what we've achieved as well. Cherish it."
McCullum, 40, was renowned as one of the most attacking players of his generation but has already suggested Stokes might boast an even more positive mindset.
Even so, the idea McCullum might be the man to pump the brakes is an unlikely one and confessed he is happy for England to come unstuck in their new approach, provided they learn from it.
"I'm aggressive but Ben's got me covered, which is saying something," he said with a grin.
"I hope we take it too far because then we'll know exactly where that line is. Until you do that, you're not really sure."
England do not have to wait long for their next to chance to challenge themselves, taking on India at Edgbaston in a match rearranged after a COVID cancellation last summer.
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