Respect for Tonga's royal family runs deep in the kingdom — but how did they help ward off colonial powers?

On hot roads that bake under the Tongan sun, a black London taxi cab used to split the traffic like it was parting the Red Sea.

It was the personal vehicle of the late King George Tupou V.

And the carefully polished cab was at complete odds with its surroundings.

Among beat-up old utes and second-hand sedans, every now and then the black cab would emerge and iron the road as the royal headed to his next appointment.

It was not the only unusual personal choice made by the late king, who was known for his posh British accent — something he acquired through his education in England — and his mastery of several languages.

King George Tupou V also occasionally sported a monocle, wore plinth hats, and had a fondness for military pomp and ceremony.

Western media outlets, unused to seeing a Pacific monarch, often described him as "eccentric", "flamboyant", and "colourful".

But far from being an object for derision, the late king and his personal style continued a long tradition that explains Tonga's status as the only Pacific nation not to be colonised.

This year, the kingdom marks 150 years since its monarchy gave up some of its powers and drafted a constitution that remains alive today.

Historians today say it's a move that helped ward off colonial powers, who recognised the system of government Tonga's rulers created — and who respected the European dress they adopted.

It's a story of adaptation that has made Tonga's monarchy the last in the Pacific.

And it explains why respect for the royal family runs deep for Tongans — who regard it as a symbol of the sovereignty they never lost.

So how did Tonga's rulers come to wear English clothes, and how did they become an enduring symbol of Tongan independence?

Fale 'o Tupou (House of Tupou)

That deeply-ingrained respect for monarchy has its roots in centuries-old history.

And at one time, it resembled religious worship.

On the eastern side of Tonga's main island, Tongatapu, stand monuments to a time when its monarchs were like gods.

Pyramid-like structures called langi are a reminder of the country's absolute monarchy.

Paepae 'o Tele'a is one of the few that has been well preserved.

It would have taken hundreds of men to pull the stones ashore from canoes, using rolling logs.

The langi were created on the order of the Tu'i Tonga, the country's paramount ruler from a line stretching back to 900AD.

And his authority carried the weight of a deity, according to local talking chief Makalangahiva.

"Some people say [the workers] were working as punishment," he said.

"No. There was only one Tu'i Tonga. If they were working as punishment, surely they would have killed the Tu'i Tonga — with respect to the king and to the nobles — because there were a lot more people.

"They carried out this work because of their faith — they believe they'd be blessed by the Tu'i."

It was authority that prevailed for a long time, and evolved as two additional royal houses emerged and took on political power.

But it unravelled after a royal assassination in the 1800s, and civil war threatened to severely weaken Tonga.

It was one man, Taufa'ahau, who partnered with Wesleyan missionaries and emerged from the conflict with power.

He consolidated the three royal dynasties under one crown. And he made a change that would repel the European powers colonising the Pacific.

First, he drafted a constitution that gave Tonga's people freedom from slavery, freedom of speech and religion, and let them own land.

Tongan political analyst Lupe Ilaiu said the constitution was an act of sacrifice for the new king.

"His wide powers were now limited to only what is provided in the constitution," she said.

It was based on England's Westminster system, but adapted to suit Tonga.

And when it was enacted in November 1875, it gave the people greater freedoms than before:

"The establishment then of the constitution will become a final testimony to the independence of the Tongan people forever," the king said in opening the country's parliament that year.

"It will be a means whereby the Tongans can boast of their independence like the people of Rome in days long ago."

Ms Ilau said the constitution was a major reason Tonga remained free from European colonists.

"The granting of the constitution was one sure way of gaining internal national recognition as a nation and something that was not available to most of our neighbouring Pacific Island countries and the rest of the world," she said.

The new king also took on a name used by British kings, George, and dedicated the country to the same Christian god he worshipped.

And he almost always donned European clothes.

'Forcing power to see power'

Of the small handful of images showing King George Tupou I, only one shows him in traditional Tongan dress.

In most of the black and white photos of the monarch, he's either in the suits, shirts and long pants worn by Europeans, or in Western-style military uniform and medals.

He would wear the traditional mat, folded around the waist, on state occasions, according to the Wesleyan Juvenile Offering in 1852.

"It is very cumbersome, and not as becoming as his usual costume," the journal said.

But today's royal family successfully combines Tongan traditional dress with Western attire, and Tongans, including King George Tupou VI and Queen Nanasipau'u Tuku'aho proudly, wear the ta'ovala — a woven mat — around their waists.

As for the gold crowns and ermine capes, they only make an appearance on Coronation Day.

To some, it's all been part of Tonga's success in resisting colonisation.

Tongan writer Dr Karlo Mila's called it "a strategy of resistance" in her poem, A Tongan reflection on Tino Rangatira:

Perhaps no king has embraced British fashions quite like the current monarch's predecessor and brother — the black-cab-borne King George Tupou V.

As one woman told Kiwi scholar, Areti Metuamate, outsiders saw him as a bit "odd".

"But I was proud of him and his colorfulness," she told Metuamate.

"So he loved fancy clothes and spoke French and German? What king or queen doesn't speak more than one language and wear the best clothes?

"Some want him to walk around wearing coconut sandals and a ta'ovala. Why? It's the 21st century man! Why can't the King of Tonga be modern too?"