But then Bairstow and skipper Ben Stokes ripped the New Zealand attack apart in devastating fashion, hammering 102 in the first nine overs after the interval.
Stokes was hampered by a knee injury, but with Bairstow taking the lead, their partnership was worth 179 runs in 20.1 overs.
Bairstow flew to his century in 77 balls -- the second fastest Test century by an England player, one ball slower than Gilbert Jessop’s record against Australia at The Oval in 1902.
“It was great fun, one of those things when you get in that mood, just go with it. Do or die, so you’ve got to do,” said Bairstow.
The Yorkshireman finally departed to a standing ovation after he was caught behind off Trent Boult, having hit seven sixes and 14 fours.
Stokes and Ben Foakes took care of the remaining 27 runs to soak up the cheers of a crowd that had been given free tickets for the match.
The win was a vindication of the positive approach taken by skipper Stokes and new coach Brendon McCullum -- himself known for aggressive attacking cricket.
“Today was set up perfectly for how we want to go about it, run into the danger rather than back away or stand still,” said Stokes.
New Zealand were left to ponder how they had lost the match after making 553 in their first innings but their decision to attack Bairstow with short pitched bowling after tea -- and to stick with that approach while he peppered the stand -- will feature heavily in their post-mortem.
The tourists were without their captain Kane Williamson in this Test, after he tested positive for Covid, and seamer Kyle Jamieson was unable to bowl in the second innings due to a back injury, but this will be a tough loss to recover from.
“At Tea it was still in the balance but the way Jonny and Ben were able to play was outstanding,” said stand-in skipper Tom Latham.
“A great surface to bat on, wickets were hard to come by, to be in with a chance at Tea, a couple of wickets there and it’s a different story. A bowler down doesn’t help but they kept coming back, and wanting the ball.”