There's something surreal about how quickly it's all happened; a Sunday afternoon media conference with Hipkins and Sepuloni at the podium, and to think one of Jacinda Ardern's last public acts as prime minister was to auction off a signed Hansard copy of her "arrogant prick" comment with ACT leader David Seymour.
Her bombshell - only last Thursday - immediately sparked intense discussions among MPs about the future. Once the matter of leader was settled, attention turned to how the party would best represent Māori, women, Auckland and Pasifika - all wrapped up in the new structure with senior Māori MP Kelvin Davis staying on deputy leader of the party wing.
Grant Robertson will keep the role of finance minister but has stepped aside as deputy prime minister to make way for Sepuloni, who is of Samoan, Tongan and New Zealand European descent. Like Ardern, Hipkins and Robertson she, too, is from the class of 2008.
The MP for Kelston, Sepuloni has been a steady pair of hands in the social development portfolio and makes history as the first Pasifika deputy prime minister.
Her Cabinet colleague, Aupito William Sio, could barely contain his emotion as he made his way into the caucus room, wearing his ula fala - a necklace worn by Samoan high chiefs for times of celebration.
"It's historic, the dreams and aspirations of many of our parents and grandparents."
Sepuloni talked about breaking the news to her sons, welling up as she spoke about their messages of pride; but she said she'd held off telling her father, who had been in Samoa this past week, as she "didn't want to run the risk of him telling the whole village over there before he returned".
Hipkins took the opportunity to address his own personal situation, as the father of two young children, one at school and one at kindy, talking about the break-up of his marriage last year.
"It's bloody hard, families come under an enormous amount of pressure.
"A year ago, my wife and I made the decision that we would live separately, that we would do everything we can to raise our children together, we remain incredibly close, she's still my best friend," he said.
"But we have made that decision in the best interests of our family. My view is that the only people whose business that it is, is my own."
Hipkins said he would not putting his children into the public arena and asked their privacy be respected.
As to the governing side of things, he said the government would focus on the "bread and butter" issues, the cost of living pressures facing low and middle income New Zealanders and small businesses. No different in the messaging coming from Ardern at the end of last year, but a deliberate emphasis on getting back to basics.
What that looks like, however, has yet to be articulated.
Looking at the leadership contest, it was swift and bloodless, carried out with little apparent political damage - either internally or to the Labour Party brand.
The speed and professionalism with which MPs executed this transition is in stark contrast to what Labour inflicted upon itself in the post-Clark years, and then the National Party in opposition after that.
There was a clear motivation to get this sorted by the Sunday 1pm deadline. Firstly, it meant the caucus had 100 percent say; if it had gone on to the next stage, MPs' influence would have been diluted, getting 40 percent alongside the membership at 40 percent, and affiliated unions at 20 percent.
The other risk is the longer the contest goes, the less patience the public has for politicians talking about themselves and the greater risk of open conflict or criticism between contenders. Anyone involved in the Labour contests done that way in the past will also remember how long they took, and there's simply not the time for weeks of campaigning in this climate.
Andrew Little stepped aside as leader in 2017 for Ardern, and after some bruising leadership battles of his own, said this contest had been "encouraging".
"We've had, in our history, some pretty rocky experiences ... this indicates a new level of maturity, a real unanimity of purpose," he said.
Sepuloni also remembers those times well, describing former leadership battles as a "rough ride".
"It's a relief that we are in the place that we are and we have been for quite some time, and it is a unified caucus."
She said there was "no need to explain how it's been in the past ... it's played out very publicly and we certainly have all learned lessons from that".
Hipkins and Sepuloni will be sworn-in on Wednesday, but he will hit the ground running today with the regular round of morning media interviews.
He will go to Rātana tomorrow, accompanying Ardern on her last outing as prime minister. On Wednesday he will chair his first Cabinet, then front the media briefing. The rest of the week will be taken up with meetings with business leaders in Auckland and starting work on the policy reset and Cabinet reshuffle.