They have been coming to the capital’s central park for 6 weeks now, the striking civil servants holding out for a pay increase. It's here last Wednesday that I meet Sione Vuna Faotusia, known to all-comers simply as Vuna, the secretary of the strike committee.

SIONE VUNA FAOTUSIA, STRICK COMMITTEE: This is the beginning of the change in Tonga. It ain't going to change until this whole system is changed.

Some days later Vuna will tell me just how serious this dispute is becoming, revealing that radicals are talking about murdering the royal family. But at this first encounter, he stresses the strike's political importance.

REPORTER: So this strike isn't just about a pay rise?

SIONE VUNA FAOTUSIA: No longer. This is for the whole system. It's no longer for the pay rise. The pay rise is still the edge of the sword, but the movement is much more than that. Because we know what the problem is, the problem is the system of government that we are having right now.

That system is headed by King Taufa'ahau Tupou IV, 87 years old and in failing health. He's appointed his son, Prince Ulukalala Lavaka Ata, as Prime Minister. His eldest son, and heir, Crown Prince Tupouto'a and the Princess Regent Pilolevu also wield considerable political power, as well as having acquired many of the country's key economic assets. The King appoints the executive government, its 16 ministers in turn dominate the country's small parliament. Until recently, Clive Edwards was one of those ministers.

CLIVE EDWARDS, PRO-DEMOCRACY MP: Ministers are afraid to make decisions that might run counter or contrary to the perceived wishes of His Majesty or his royal commands, or the perceived wishes of the Crown Prince or the Prime Minister. And as long as you have a state of affairs that exists like that, this country is not heading anywhere at all.

The last few weeks has seen an escalation in tension. The morning I arrive in Tonga, someone has torched one of the King's houses, his traditional residence, 30 minutes from the capital. Not long ago, such an attack on royal property would have been unimaginable.

WILLIAM, WITNESS: I'm a direct witness of what happened last night. We live nearby. We came about 4:30. There's a hole in the fence and the police last night found a bottle of gasoline.

REPORTER: A bottle of gasoline?

WILLIAM: A bottle of gasoline. It's empty.

The government asserts the incident is related to the striking civil servants.

GOVERNOR AKAUOLA, CABINET MINISTER: There's no doubt that people are being fuelled. Whether these people that are actually doing the burning are themselves strikers...

REPORTER: Do you suspect they are?

GOVERNOR AKAUOLA: No, I don't.

REPORTER: Do you think they're under the instructions of strikers?

GOVERNOR AKAUOLA: Very, very possible.

With the possibility of more violence, the government isn't ruling out using the army against the strikers.

GOVERNOR AKAUOLA: If the damage continues, then the government is bound to act.

REPORTER: So the government reserves the right to use the army if needs be?

GOVERNOR AKAUOLA: Well, put it this way, there is legislation in place, including anti-terrorist legislation, which is there, which the government will look at.

Vuna is aware of the threat to use the army but says such a move would backfire.

SIONE VUNA FAOTUSIA: Definitely. Definitely. Isn't that what happened in the rest of the world? Once they use the military, people will have to use the same force against it.

REPORTER: Hi, Vuna. How are you doing? What's happening?

SIONE VUNA FAOTUSIA: We haven't heard anything from the Princess Regent.

I've arrived in Tonga at a pivotal time - the strikers have decided to reject New Zealand arbitration. With the King and Crown Prince out of the country, they're placing their hope in the Princess Regent, Pilolevu.

SIONE VUNA FAOTUSIA: But he could very well decide on our favour. This is the only time for her to make a decision, because if she fails to make a decision, like, what they say, Tonga hasn't been with a leader for so long. We need leadership.

Vuna plays a central role in deciding strategy. He comes from a noble family, has studied in Hawaii, London and Sydney and holds a senior job in the Justice Department. It's only later that he tells me how committed to the strike he's become

SIONE VUNA FAOTUSIA: There's always been some sacrifice. And I believe it's the same here in Tonga. There will be. You have to sacrifice your time, your energy, maybe even your life, maybe even your life. But I believe that's the way it should be. If you think it's that important, you have to sacrifice.

So far, the pro-democracy movement has been largely peaceful - marches of up to 10,000 people moving through Nukualofa. Recently they've been in support of the strikers, before that it was increases in the price of electricity that brought people onto the street. That's because a few years ago the power company was privatised and bought by the Crown Prince.
He's sacked workers, hiked the price of power and paid himself a salary of something like $700,000 a year. He also owns the brewery, an airline and the mobile phone company and lives in this modest home on the outskirts of the capital.

SIONE VUNA FAOTUSIA: Honestly, he doesn't have any principle at all. The old man, the King has got principles. He has been a good king all along, he worked for the country. No, his children, I don't think so. The people are still respecting the King, but not his children, no.

But Vuna is only half right, as I learn when Princess Pilolevu arrives unannounced at the strike rally in the park.

PRINCESS PILOLEVU, (Translation): I'm not here because of the government. But rather I'm here this morning as a mother. You are like weeping children. Children separated from the wisdom of the mother.

The effect of the royal presence is astounding. The crowd breaks into a spontaneous rendition of the national anthem. The Princess offers nothing new, yet when she leaves the crowd seems elated.
The moment captures the internal conflict within many Tongans - they want democracy, but can't quite reject the traditional fealty towards the royal family. Perhaps that's why some may consider violence as a circuit breaker.
On the evening before I leave Tonga, Vuna finally confides in me what he's been hinting at over the past few days, that violence may soon be directed at the royals themselves.

SIONE VUNA FAOTUSIA: People start talking about violence. Violence, maybe, is one possible means of settling this dispute, even though we don't want to go that far, but...we can't stop them.

REPORTER: So who's talking violence?

SIONE VUNA FAOTUSIA: Oh, there are a group of people. They don't agree with what we are doing. They say what we are doing is too slow - too many hymns, praying, religion is not the answer.

REPORTER: So what do you say to those people?

SIONE VUNA FAOTUSIA: You can do it, whatever you want to do, you can go out and do it but don't associate with us because our association is peaceful.

REPORTER: So what sort of violence do you think they might... So you're not just talking about burning down buildings?

SIONE VUNA FAOTUSIA: No, no, no. Not just burning. They are talking about eliminating people.

REPORTER: So killing people?

SIONE VUNA FAOTUSIA: Killing people.

REPORTER: Killing who?

SIONE VUNA FAOTUSIA: There are a few people. All I know, I mean, they are talking about the royal family.

REPORTER: They are talking about assassinating the royal family?

SIONE VUNA FAOTUSIA: Oh, yeah, they are talking about the royal family. That's where they want to start. You know, even though if you don't want it, but that's what they want. Heads start rolling.

At the end of each day the strikers go home, leaving only the hard-core kava drinkers to continue the vigil in the park. Whether talk of killing the royals is merely bluster or a serious threat, it shows the stakes are rising. The strike shows no sign of resolution and the government no sign of compromise. It seems inevitable that when the old King dies, Tonga's absolute monarchy will face its most serious challenge yet.