New Zealand Prime Minister Jacinda Ardern went to see the Queen lying in state after becoming one of the first foreign leaders to arrive in the UK for the funeral.
Television footage showed Ms Ardern stopping to curtsy as she filed past the coffin at Westminster Hall on Friday.
She will be one of the 500 world leaders and dignitaries who will be attending a Buckingham Palace reception that is being hosted by King Charles on Sunday ahead of the Queen's funeral the following day.
Millions of people from all backgrounds are visiting London for the funeral as well as the heads-of-state which has led to a major security operation.
Ms Ardern confirmed that she will meet King Charles and the Prime Minister Liz Truss, in a press conference after arriving in the UK, saying she will "share the sorrow that New Zealand has" with the new monarch.
"I'll simply share the sorrow that New Zealand has and pass on our deepest condolences," she said.
"At the end of the day, although this is a period of transition for him, he has also lost his beloved mother. For us and New Zealand, that's first and foremost."
The visiting PM said the Queen's death and new King will be the "focus of conversation" when she and Ms Truss meet.
"I am sure we will also transact our relationship as well, but it is all within the context of the week of mourning that the UK is currently in," she said.
Then meeting Prince William will be an opportunity to repay his support of New Zealand in 2019, when the royal flew to the country following the Christchurch massacre, Ms Ardern said.
"The Prince of Wales has always been there for New Zealand in its times of grief," she said.
"He's been there for us in our times of grief and so this is a time for us to be there for him and his family too."
With the arrival of heads-of-state, Downing Street has declined to describe the conversations with allies as formal bilateral meetings, and instead portrayed them as chats to offer condolences over the Queen's death, during which politics is likely to come up.
The Prime Minister's official spokesman said: "There won't be formal bilaterals in the way we normally recognise them.
"But we will have a significant number of world leaders, heads-of-state in the country. She will be meeting a small proportion of those over the weekend.
"These will be opportunities to discuss memories of Her Majesty, but in some instances it will be the first time they've met since she became Prime Minister."
A UK meeting with US President Joe Biden, who will attend the funeral with First Lady Jill Biden, would ease the pressure on Ms Truss's expected visit to New York for a UN summit next week.
Chevening will be used as one base for meetings rather than the Prime Minister's country residence of Chequers, which is said to be undergoing routine maintenance work after Boris Johnson's exit.
French President Emmanuel Macron confirmed his attendance at the funeral after offering his country's condolences in a call to the King.
Mr Macron tweeted about the "unbreakable" ties between France and the UK as he promised to "strengthen" the relationship between the UK and France by "following the path" of the late Queen.
It is unclear whether he will be among the world leaders Ms Truss will meet, but if they do it will be a chance for her to clear up where their relationship stands.
During her campaign to become Tory leader, she sparked controversy by saying the "jury's out" over whether Mr Macron is a "friend or foe".
There have also been suggestions she could speak to Irish Taoiseach Micheal Martin on the margins of the funeral, amid strained relations between the two countries over the continuing row about the Northern Ireland Protocol.
