By Sarah Robson
When New Zealand and the Cook Islands came up with the concept back in 1965 of self-governance in free association, they were laughed at.
Despite the doubters, the two Pacific nations are coming together to celebrate 50 years of their world-first constitutional relationship.
Prime Minister John Key touched down in Rarotonga on Monday (local time), accompanied by a large delegation of government ministers and other MPs, including Labour leader Andrew Little and NZ First leader Winston Peters.
Mr Key has held talks with his Cook Islands counterpart Henry Puna and the pair canvassed a wide range of issues, including New Zealand's estimated $42 million aid contribution over the next three years.
Much of that money will be spent on infrastructure, solar power, education and health projects.
"One of the things both New Zealand and Australia have been trying to do for our friends across the Pacific is bolster their economies and give local people much greater opportunities, particularly young people, to stay," Mr Key told a press conference.
"A big part of that here is in tourism and fisheries, where New Zealand has been very actively involved trying to support the Cooks."
Mr Puna says the Cook Islands' relationship with New Zealand is as strong as ever.
"When we started off 50 years ago, free association was something totally new to the whole world, never been done before," he said.
"New Zealand and the Cook Islands embarked on a new journey that really made a lot of people laugh at us, they thought and they said it'll never work. But hey, we're celebrating 50 years of it."
To mark the constitutional milestone, the New Zealand Government will foot up to $11.7M of the bill to rebuild the Cook Islands' national secondary school, Tereora College.
The main celebrations will take place on Tuesday (local time) - Constitution Day - and thousands of Cook Islanders are expected to turn out for the occasion.
Self-government in free association isn't the same as full independence.
Cook Islanders are New Zealand citizens, have New Zealand passports and use New Zealand currency.
But the Cook Islands government is free to make its own laws and conduct its own affairs.