By coincidence, and perhaps the humour of fate, National leader Christopher Luxon and former leader Simon Bridges happened to be in London this week discovering leadership implosions are much more fun when you are a spectator rather than a participant.
That is the first and most obvious lesson totake from watching British Prime Minister Boris Johnson going down in a blaze of in-glory and the attendant sideshows around it.
It cost Luxon a few appointments. He had been scheduled to meet Conservative ministers Michael Gove, Nadhim Zahawi and Amanda Milling.
Instead, Gove was busy telling Johnson to resign and getting sacked, Zahawi was being promoted to Chancellor of the Exchequer and Foreign Secretary for Asia Amanda Milling was busy changing from a Johnson backer to a more flexible position.
Luxon did get to see the woman Johnson replaced, former PM Theresa May, and reported she was "in good spirits".
On Johnson, he stuck to the same line Ardern used when giving her verdict of the events: it was a domestic matter for the UK and whatever the outcome, New Zealand would have a strong relationship with the UK.
It is bad form to publicly pick favourites or wade into the goings-on in another country.
It is probably fair to assume Ardern will not weep for Johnson. He was a Conservative, and not really Ardern's cup of tea along with it.
Ardern was in Australia meeting PM Anthony Albanese when Johnson resigned. Her relief at having a Labor Prime Minister there after five years of Scott Morrison is very thinly veiled.
But whatever the views of Johnson's style and politics, Ardern and some former New Zealand Prime Ministers may be quietly reflecting New Zealand has lost one of the best friends it has had in 10 Downing Street.
That is not to say others are unfriendly - they are right that the relationship will remain strong, whoever takes over.
But Johnson, throughout his colourful political career, has been consistent and vocally enthusiastic about New Zealand and his belief the United Kingdom's doors should be more open to New Zealand.
The reality of domestic politics stopped him yanking open those doors to the extent he once proposed: as London mayor he had promoted totally visa-free movement between the UK and Commonwealth countries including New Zealand, Australia and Canada.
But one of his very last acts as Prime Minister during Ardern's visit to London last week was extending the visa that allows younger New Zealanders to live and work in the UK. It will now cover a wider age group, and last for three years instead of two.
After Brexit, one of his first assurances was that New Zealand would be no worse off as a result - and, in fact, was likely to end up better off.
Theresa May was first to put New Zealand at the top of the queue for a post-Brexit free trade agreement - she did that when former PM Bill English visited in 2017.
But it was Johnson who saw that to fruition. The free trade agreement with the UK is far more generous than the recently signed New Zealand–European Union effort. That was as much for the UK to prove it was a good trading partner as for New Zealand's benefit – but the New Zealand side quietly acknowledge it perhaps might not have been quite so good had a different Prime Minister been at the helm.
There are some hopes Liz Truss will take over as Prime Minister as the best bet for New Zealand's interests – there is already concern the changeover will at least delay the progress of the recently signed UK-New Zealand trade deal and Truss was the trade minister who negotiated it.
Johnson's end has highlighted just how stable things are in New Zealand, where opposition leaders have fallen as a result of scandals or incompetence or failing to be popular – but Prime Ministers have tended to stay in the job. We have not had a Prime Minister unwillingly leave office since Jenny Shipley rolled Jim Bolger in 1997. The only other change outside an election was John Key choosing to step down in late 2016. They have not gone as a result of scandals or integrity issues.
Johnson is a salutary reminder that more than policy and delivery count – morals and integrity also play a part.
The second lesson is that a mandate from the voters at an election has its limits and is not an immunity card. Johnson made a last-ditch effort to survive by throwing the mandate card on the table, pointing to the 2019 election result in which he stormed home, saying that gave him the mandate to stick in the job.
He had a point, to an extent. The British public were not voting blind when they picked him.
They knew well Johnson's character, and because of that he got more leeway than politicians who portrayed themselves as virtuous souls of probity and then acted otherwise.
Johnson won his election on the Brexit platform - and ended up dealing with Covid as well - while Ardern won hers in 2020 on the Covid platform.
The lesson for her from Johnson's demise is that mandates from the voters are not a license to do anything you want – nor necessarily a mandate to do everything that was in your manifesto, especially the bits that were in the small print.
For very different reasons than those that applied to Johnson, that warning is also being sent to Ardern through the polls.
As for Johnson, in his valedictory National MP Nathan Guy recalled Johnson telling him he drank Marlborough sauvignon blanc - "gallons of the stuff". Cheers Bojo.