England comfortably chased a target of 167 to win the third and final match in Karachi, adding to their wins in Rawalpindi and Multan.
The high-risk high-reward approach that has brought England nine wins from 10 Tests has been dubbed ‘Bazball’ in a nod to McCullum’s style but the New Zealander shifted the credit to new captain Ben Stokes.
“The side is very much in the image of the skipper,” McCullum told Sky Sports. “He wants the guys to go out there and play with as much freedom as they can.
“He has identified that taking away that pressure and fear of failure allows the talent to come out.
“And what we have seen over the last seven to eight months is that skill and talent is not in question with this England side.”
That fearlessness is not limited to the pitch, however, with McCullum also showing some moxie on the sidelines.
After a shirt he had signed for a fan got stuck at the top of a chain link fence on Monday, the 41-year-old head coach wasted no time in scaling the barrier to retrieve it before throwing it over the other side.
Prior to the tour, England had won only two Tests in Pakistan and it was their first series win in the country since 2000-2001.
McCullum said he was “incredibly proud” of the team.
He also praised 18-year-old Rehan Ahmed, who became the youngest bowler in men’s test history to take a five-wicket haul on debut.
“He’s got a real future,” McCullum said.
“He’s been on the radar for English cricket. It took some courage from Stokes to thrust him into this side. The more we’re willing to do that, the better for us.”