The Prime Minister will wrap up her European tour overnight, visiting Prince William in London.
The event is closed to the media, but Jacinda Ardern always visits a member of the royal family when she is in London.
Ardern's final event of the trip is a speech at London's Pride parade, where she is expected to encourage attendees to visit New Zealand.
Ardern earlier talked up the strong connections between the UK and New Zealand during a packed visit to London on Friday in which she met Prime Minister Boris Johnson and reflected on her OE working for former Prime Minister Tony Blair - she even talked up the two countries' shared love of British game show "The Chase".
But the visit took a slightly darker turn, with Ardern using a major foreign policy speech to warn of "growing unrest" in the Pacific, which she said was partly down to growing Chinese assertiveness.
Her first stop was 10 Downing Street, where she signed a new visa deal with Johnson. The deal will expand the working holidaymaker scheme that allows New Zealanders and British citizens under the age of 30 to live and work in each other's country for two years.
Under the terms of the new scheme, the age limit has been lifted to 35, and the length of the visa has been extended from two to three years. The new rules will kick in by 2024.
"The UK is one of Aotearoa New Zealand's oldest and closest friends and partners," Ardern said.
The visa changes "reflect the depth of the NZ-UK relationship", she said.
Ardern had lunch at Downing Street with Johnson. They were later given a performance by Ngāti Rānana, the London Māori cultural group, in the Downing Street Garden.
For Johnson, the visit was overshadowed by yet another domestic political crisis. Johnson has been out of the country for a week, and has faced persistent questions about his leadership. On the last day, his deputy chief whip resigned after admitting he had "embarrassed [himself] and other people" after he "drank far too much" - it has been alleged he groped two men.
As Johnson escorted Ardern into Downing Street, British media could be heard asking whether he was "drowning in sleaze".
Ahead of their meeting, Johnson said he was pleased to welcome Ardern to the UK on her first visit there since the pandemic.
"I want to say in particular a word of thanks and praise to New Zealand for the very strong line you take on Ukraine," Johnson said.
Ardern drew attention to the fact that part of New Zealand's response to Ukraine was UK-based New Zealand forces training Ukrainian soldiers in the use of artillery.
Ardern appeared last night in New Zealand time on Lorraine, a British morning TV chat show that attracts more than 1 million viewers an episode on ITV.
Talking on the show, which is hosted by popular Scottish broadcaster Lorraine Kelly, Ardern said: "We're actually already open, anyone in the UK you can travel now. I'll put a plug in, your winter is our summer so make those plans.
"Having been to Scotland though I can say summer is a little more summery in New Zealand, as much as I love places like Scotland."
Ardern spoke of her love for New Zealand's scenery, doing her best in an ongoing selling pitch that tourism operators will hope will help inject billions of dollars into the nation's Covid-hammered industry.
The total tourism expenditure – international and domestic - dropped by $15.6 billion in the 2021 financial year, to $26.1b compared with the 2020 financial year, which correlated with the arrival of Covid-19.
Total international visitors dropped to just 52,690 last year, down from 3.6 million prior to Covid-19's spread through New Zealand which led to the tightened borders.
"I would like to think I can be objective, it [New Zealand] is just the most beautiful place," Ardern said on Lorraine.
"What I love as well as you can get that combination of being in cities but then being in close proximity to nature, beaches, amazing walks, nature tourism and now food and wine - it's hard to have a bad meal."
Talking later on a Facebook Live post to her followers, Ardern spoke of her appearance on Lorraine.
"This morning I had a quick interview on a television show here in UK where they showed beautiful images of New Zealand while we talked about the reopening and inviting people to come on over."
She also spoke of how important it was to spread the message during her trip to Europe that New Zealand was now open again as a viable tourist destination.
"We had three main goals for this trip, as had been the case with others so far: really focused on making sure that the world knows we are open, that we are open for business, that we are open for tourism and that we are very keen to welcome visitors back.
"So we have had events in Brussels, we have an event here in London tonight and it is all about showcasing New Zealand products but also inviting people to come, to come and see us, and help with the rebuild of our tourism sector."
On Lorraine, she was also questioned about the stance her Government took as the country grappled with the outbreak of Covid-19.
That has included lengthy lockdowns – with the Auckland region enduring the most - closing the borders, and later the introduction of mandates for vaccines and masks.
She stood by the policies she introduced, saying what had been done in New Zealand had saved lives.
"We're open and I think for everyone, there was no response to the pandemic that was without cost.
"It was either an awful and horrific cost to human life or as we predominantly felt the cost of it being hard for people to move around.
"You could come and go but we quarantined and because of quarantine it was limited space.
"It was hard for everyone, but we came through it with much fewer hospitalisations and loss of life than most."
When asked by Lorraine whether in hindsight things could have been done differently, Ardern responded: "Of course. If you look back on something and you can't think of something that you would have changed you're probably not looking hard enough.
"So absolutely. But the overall strategy, no, because I know it saved lives, I know it did."