Jacinda Ardern has met Queen Elizabeth II at the Commonwealth Heads of Government meeting.
The Prime Minister was one of the 53 member states that was at the opening ceremony at Buckingham Palace on Friday morning (NZT). She was one of only four to meet Her Majesty in a 20-minute private audience, reserved for new Commonwealth leaders.
It is the first time she has met the Queen, accompanied by partner Clarke Gayford.
While in London she has also attended a top-level intelligence meeting to discuss growing international tensions with Russia.
The meeting of countries belonging to the Five Eyes network was a late addition to Jacinda Ardern's European tour.
She sat down with her British, Australian and Canadian counterparts amid accusations of Russian interference on millions of computers around the world.
Before that, Ms Ardern had a face-to-face with UK Prime Minister Theresa May at Downing Street, with the pair discussing trade and international tensions - including Syria and the Salisbury nerve agent attack.
Ms Ardern also met royals Prince Charles and Camilla, Duchess of Cornwall and London Mayor Sadiq Khan.
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She arrived in London straight from Germany, where she met with Chancellor Angela Merkel and discussed trade, international relationships and the Syrian conflict.
Ms Merkel said Kiwis should "be proud" of Ms Ardern after what she described as an "interesting and fun" first meeting.
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Ms Ardern will attend a banquet and deliver a toast to the Commonwealth at around 7:30am on Friday (NZT).
She is expected to wear a korowai [cloak] to the dinner, and end her toast with a Maori proverb.