Senior England batsmen Alastair Cook and Ian Bell took responsibility in the final session against tricky lines and consistent lengths to establish an unbeaten partnership of 49 for the third wicket.
New Zealand created an intimidating atmosphere as McCullum stacked the slip cordon and catching positions, as is his modus operandi. Boult got a ball to angle away from Adam Lyth (Southee pocketed the spoils at third slip) and Southee delivered another candidate for 'ball of the day' to dismiss Gary Ballance for a duck. The ball pitched on middle but deviated to take the top of off stump.
Cricket and justice merged to start the day as Williamson became the 18th New Zealander to earn a place on the visitors' honours board.
The achievement was warranted. Williamson plays the game in a spirit in which you wish cricket was always conducted.
He warmed-up in a relaxed fashion, even appearing to drop his wallet on the outfield, prompting one dag to suggest he was ready to "cash in".
He did. Williamson was clinical in reaching a mark which links him to the select group of Don Bradman, Sachin Tendulkar, Alastair Cook, Garry Sobers, Neil Harvey, Graeme Smith and Javed Miandad, as players who have scored 10 test centuries before the age of 25.
Kane Williamson joined an elite club with his 10th test century before the age of 25.
Light rain delivered an early lunch and the players were absent for almost two hours.
Williamson eventually reached 132 before edging to short leg off Moeen Ali, leaving New Zealand 470 for six. Watling guided the New Zealand tail on his way to 61 not out. Extras also had a blinder reaching 67, the fifth highest total in their 138-year career; England's bowlers strayed legside too regularly.
On 92 to start, Williamson had five runs by the end of the opening Ali over. He played the percentages, pushing balls through the covers, backward of point and to mid-on. The next three came when he got into line behind a slightly over-pitched ball from Jimmy Anderson. The delivery offered enough width for Williamson to guide it to the vacant third man.
In customary fashion he sauntered to the Pavilion end, removed his helmet, and raised his bat undemonstratively to the dressing room. Teammates and staff poured onto the balcony to deliver a raised-arm ovation. Partner Ross Taylor arrived to shake gloves.
Significantly, every time Williamson has scored a test century before now, New Zealand has never lost.
He has the highest test average, 47.25, for any New Zealander to have played more than 15 test innings. His average from 16 innings in the last year is 92.46 but, intoxicating as the numbers are, it's more about the character and confidence he imbues in the team. His humility, determination and influence are, and should continue to be, a core reason why this New Zealand team stays successful.
"Overnight, knowing I was close and with so much spoken about the honours board, it plays a bit on your mind but you've got to get on with the job. It was nice to cross that line with the history that goes on here.
"There's always a quiet buzz that sounds like everyone is talking to their mate next to them, then a shot or a wicket occurs and they cheer which makes you realise everyone is watching closely."
Read more: Williamson delivers Lord's masterclass
Williamson survived two chances. One came on 92 in the penultimate over of the second day when Ali lured him from the crease and wicketkeeper Jos Buttler missed a stumping. An edge fell short of first slip on 106 and another flew through Bell's hands on 120.
Taylor suffered less fortune flicking a faint edge down the legside on 62, but his professionalism helped guide New Zealand to their dominant position. His half century made it the second time in tests that each of New Zealand's top four had scored more than 50. The top five achieved the feat against Pakistan in Lahore during the second test of 1965.
Ross Taylor and Kane Williamson added 189 for the third wicket
The 189-run partnership between Williamson and Taylor was the third highest for the third wicket at the ground, behind Martin Crowe and Bruce Edgar's 210 in 1986 and Bevan Congdon and Brian Hastings' 190 in 1973.
Taylor's dismissal brought Brendon McCullum to the wicket, who treated the venue as his personal playground on the way to 42 off 38 balls. A miscued pull top-edged to Joe Root at third man, gifted Mark Wood his maiden test wicket.
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Until McCullum's arrival, England had fought back with the second new ball. They appeared to pitch up more to maximise the swing. An example was the stymied progress of Williamson who made 12 runs from 64 balls after reaching his century in the 79th over.
"Williamson scored at ease the night before, but today he didn't score with that same freedom," said Wood.
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