In October 1769, the Maori of Aotearoa witnessed a luminous sight on the horizon.

An extraordinary craft, high above the water, blazed from the sea. Pinpricks of light shone from small squares along its body. White sails billowed.

Word spread up and down the east coast of New Zealand before the Endeavour reached land: a leader in strange clothing, captaining a strange ship had arrived.

But the name they spoke of was Tupaia.

At first some locals had thought the ship was a giant bird, or even an island. ( Illustration: Mat Tait/Supplied: Auckland Museum )

Two months earlier, having sighted the June transit of Venus, HMB Endeavour had departed Tahiti.

Lieutenant James Cook unrolled his "special orders" — to sail south in search of the great southern continent.

Alongside his crew of talented English scientists was Tupaia, a Polynesian high priest and star navigator, and his young apprentice Taiata.

Botanist Joseph Banks had secured their place on the ship.

During the Endeavour's four month stay on Tahiti, Banks — fascinated by island culture and ceremonies — had developed a strong friendship with Tupaia.

A drawing by Tupaia of a group of musicians from the Society Islands. ( Supplied: British Museum )

When it was time to depart, he convinced Cook that Tupaia's knowledge of the surrounding islands and his authority amongst his people would be helpful to the voyage.

As a sweetener, Banks offered to pay for the Polynesians' board on boat and share his cabin.

Tupaia's people had recently been defeated in war by the neighbouring Bora Bora people, and had lost their land.

He was keen to get help from the British to win back his home island of Raiatea.

'We wake to see where Tupaia will bring us to next'

Cook had seen Tupaia's navigational skills first hand, and virtually as soon as they departed Tahiti on August 9, 1769, he let the Polynesian pilot the ship through the Society Islands.

James Cook's chart of the Society Islands which was copied from an original document by Tupaia. ( Supplied: British Library )

Historian Dame Anne Salmond says Tupaia knew the islands well. He knew the depth of the water, and where the reefs were.

"Bearing in mind that that was the only ship that Cook had on this voyage, allowing a local person to pilot the ship was a big call," Dame Anne says.

"So there was a lot of trust already in his navigational abilities."

Historian and emeritus professor Geoff Irwin says he's sure Cook paid attention to Tupaia.

"He knew what the winds were. He knew that more than Cook but he shared that information with Cook and Cook was able to observe what Tupaia knew," he says.

Tupaia's depiction of traditional a Tahitian longhouse, and men in canoes, made in 1769. ( Supplied: British Museum )

The crew needed supplies on their voyage and Tupaia paved the way.

He introduced the English to local chiefs and took the officers through ceremonies that allowed them to arrive safely on islands.

"It must have been clear to those on board that Tupaia was a remarkable and distinguished person of high rank," Professor Irwin says.

Tupaia suggested they sail east toward Tonga, but Cook had orders to look for Terra Australis Incognita — the unknown southern land. They sailed south.

"And today we wake up to see where Tupaia will bring us to next," Banks wrote.

That navigation was done with the stars.

"Star paths were a major feature of Polynesian navigation as well as the currents and the birds," Dame Anne says.

A dancing woman and a Tahitian chief mourner's costume. ( Illustration: Tupaia, Supplied: British Library )

A pivotal role

Following a squiggle on a chart done by Abel Tasman in 1642, the Endeavour arrived in New Zealand at dawn at Poverty Bay in what is now Gisborne.

The English thought they'd reached the "unknown southern continent", not realising this was yet another Polynesian island.

They didn't understand the local people, nor their protocols for dealing with strangers. On the first day Tupaia stayed on the ship.

A young Maori chief was shot dead by the British.

Tupaia accompanied the crew ashore the next day. He was able to understand the local Maori people, and they him.

"The East Polynesian languages are related, like the Romance languages of Western Europe. It was a tremendous boon to Cook to have someone on board who could communicate with Maori," Professor Irwin says.

Despite the improved communication there were still hostilities. More Maori were shot.

A Maori person trades a crayfish with Joseph Banks in a picture by Tupaia. ( Supplied: British Library )

"For the local Maori, it's quite clear that Tupaia was regarded as a very important figure. Probably the dominant figure on board the Endeavour," Dame Anne says.

"They thought that the Endeavour was Tupaia's ship because he was the one that could speak to them.

"He was a high priest, navigator from the homeland, and he could say what he liked about his European companions."

Word spread up and down the coast faster than the ship. Inquisitive locals came out to see the Endeavour.

Everywhere they went Tupaia heard people calling his name.

His ability to communicate with Maori reinforced his status and skills as cultural broker.

It paid off in a huge way for the British.

Botanist Joseph Banks wrote in his journal: "We never expected him to have so much influence."

Auckland Museum's Kavi Chetty says the Endeavour crew needed food, water and safe harbour and all of that had to be done through deals with the Maori.

"The argument's been made multiple times that Cook never would have made it to Australia if it wasn't for Tupaia in New Zealand," Mr Chetty says.

"The story might have gone south very quickly."

In March 1770, Cook gave up hope of finding the great southern continent and set sail for the east coast of Australia.

The mediator is marginalised

When they arrived in Australia a month later, it was a completely different culture and landscape for all on board.

Tupaia tried multiple times but couldn't communicate with the Indigenous people. They found him as strange as the Europeans.

Tupaia painted this scene of three Indigenous Australians. ( Supplied: British Library )

His role of being the cultural mediator, the translator, the diplomat was no more. His status on board the ship was marginalised.

As they travelled up Australia's coastline, he fell ill with scurvy.

The Endeavour voyage around New Zealand and up the eastern coast of Australia. ( Supplied: State Library of New South Wales )

Cook claimed the eastern portion of the Australian continent for the British Crown, naming it New South Wales.

They then sailed north to Batavia, which is now Jakarta.

Intrigued by the streets, houses and people, Tupaia and Taiata spent much time outdoors, but the city had open sewers and was riddled with disease.

Nearly all the Endeavour crew got sick, including Banks. Despite eating fresh fruit and healing from scurvy, both Polynesians also fell ill.

Taiata died first. And a few days later, on November 11, 1770, a heartbroken Tupaia died too.

Taiata pictured in an engraving by R. B. Godfrey, based on a lost sketch by Sydney Parkinson. ( Supplied: The Trustees of the British Museum )

'A forgotten figure'

Cook and Banks returned home as heroes, but Tupaia and his work were overlooked, and then forgotten.

"It was there in the original logs and journals, but for 250 years Tupaia was a forgotten figure, despite the pivotal role that he played in the voyage," Dame Anne says.

She says the same thing happened with our understanding of how the Pacific was explored.

"The world itself paid tribute to the Europeans, who came so much later and have claimed them to be the discoverers and explorers of the Pacific," she says.

"There's a kind of hubris about that. But it's also historically incorrect. "

Mr Chetty says some people like to simplify what happened, giving Tupaia all the credit and Cook none, while others argue that it was all Cook.

But he says neither side does the story justice.

"These guys [were] working together, whether they were trying to or not," he says.

"It was that mixture of skills that probably kept them both alive and got Cook to where he was."