For those curious to observe a demigod in the flesh, the body of Norodom Sihanouk lay on display in Phnom Penh until 4 February, when it was cremated. The outpouring of grief at the passing of Cambodia’s “King Father”, who ruled the country after its independence from France in 1953, brought hundreds of thousands of mourners on to the streets, some discerning his protean features in the rising half-moon.

The Guinness Book of Records nominated Sihanouk during his phase on earth as the politician who had held more official positions and titles than anyone. After his death on 15 October 2012, at the age of 89, television stations made continuous broadcasts of historic footage of Sihanouk from the 1960s, when he dominated Cambodia as its prince, prime minister and head of state. This was the period, now regarded by many as a golden age, when the saying that “Sihanouk is Cambodia” was perhaps truest.

It was also the time when my family lived there – until Sihanouk chucked us out. In March 1964, in an act of petulant frustration, he ordered a mob to attack the British embassy, where my father, John Shakespeare, worked as a diplomat. In an incident largely unreported at the time, given that western journalists were banned from Phnom Penh, the chancery offices were ransacked, eight cars were destroyed, the apartment of the head of the British Council was burned down, and the large freezer in which embassy staff kept sausages was raided. “Rocks and bricks came smashing through the windows and, most terrifying of all, frozen legs of lamb,” my father remembers.

Sihanouk was furious at the British government for buckling under American pressure and impeding his cherished plan for an international conference to preserve Cambodia’s neutrality. Desperate to keep his country out of the Vietnam war, and so, in effect, out of both communist and capitalist clutches, he had hoped that Britain would reconvene the Geneva conference in April 1964 to guarantee Cambodian independence. Britain at first agreed to do this, then reneged.

In a characteristic gesture, he exempted my father – who next day was standing in the still-smouldering embassy compound when Sihanouk delivered to him a pre-dated gift of hideous silverware. Attached was a letter from “Monseigneur”, as Sihanouk was also known, paying tribute to my father’s “obvious capacity to approach complex Asian problems with an open mind”.

Only a few days before the trashing of the embassy, Sihanouk had invited my father to join his small entourage on a private “peace mission” to Malaysia and Indonesia. What my father remembers vividly about their week together was not the military band that welcomed Sihanouk by striking up one of his compositions for saxophone, “Brise de Nov­embre”; nor the valet who was detailed to brush the divine dandruff from the royal collar; nor Sihanouk’s scathing remarks about President Sukarno’s weakness for women; nor even his sexual confidences – “I, too, have made love in my time”. The image that lingered instead was that of the aide-de-camp who followed Sihanouk wherever he went, holding a silver casket that contained the ashes of the prince’s favourite daughter.

Cambodia is a country where it is believed that the spirits – royal ones especially – live on. The spirit of his four-year-old daughter Kantha Bopha, who had died of leukaemia in 1952, tracked the King Father in the way that he is likely to go on haunting his successors.

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No one shaped Cambodia’s character and destiny more flamboyantly than the saxophone-playing, film-directing Playboy Prince. As Sihanouk joked to my father, he had “played” until ten years earlier – until Cambodia’s independence – because the French would not let him work. “But now I work all the time, as you can confirm to your government.”

We swiftly discovered, fleeing with our belongings to the Thai border, that Sihanouk’s friendly grin concealed a vein of ruthlessness. “We can smile,” he said of his people, “but we can also kill.” A general in the French colonial army told my father that the Cambodians were by far the bravest and most brutal of his troops, and Sihanouk had ambitions to be seen in this light. Weeks after we left, he ordered the execution of a dissident supported by South Vietnam to be filmed and projected in all cinemas. Further, in his overriding project to keep the country out of the Vietnam war, he started to treat Cambodia like one of his movies.

Starting roughly from the time of our departure, the idea of making films consumed him to the exclusion of other responsibilities. His biographer Milton Osborne judged that this obsession with cinema, which resulted in the Phnom Penh International Film Festival (in which Sihanouk’s entry routinely won first prize), had “real political consequences”, as it allowed his US-backed, bombastic prime minister (and, incidentally, our landlord) General Lon Nol to manoeuvre himself into power while Sihanouk’s attention was diverted and created the conditions for Cambodia’s ensuing catastrophe.

A trivial and little-known episode ignited this film mania. His mob had attacked the British embassy a week after Peter O’Toole finished shooting Lord Jim near Angkor Wat. Charles Meyer, a mysterious Frenchman who had accompanied my father as part of Sihanouk’s entourage, appeared on location one day and “darkly advised” the director, Richard Brooks, to get his company out of Cambodia by 12 March. O’Toole was convinced that some of the rioters had worked as extras in the film. In America soon afterwards, O’Toole sounded off on The Tonight Show and in Life magazine, complaining how he and his wife had had to hide in a lavatory and how he had found a snake in his soup. “If I live to be a thousand,” he said, “I want nothing like Cambodia again. It was a bloody nightmare.”

Back in Phnom Penh, these remarks incensed Sihanouk. In one of his interminable radio speeches, he denounced O’Toole’s comments as further evidence that western governments were conspiring against his country. “Stew made from snake’s meat, scorpions lurking in boots, the poverty of the people . . . that is the image of Cambodia current in the four corners of the globe.”

A different image was needed. Faithful to his reputation as the Pioneer Prince, Sihan­ouk announced that he had decided to take up the challenge: “For who is more qualified to provide such a real picture of present-day Cambodia?”

Incredible to relate, from 1964 until his overthrow in 1970 by the palindromic Lon Nol, while Sihanouk was on a visit to Moscow to seek Russian support, Sihanouk directed his best energies, energies that he ought properly to have devoted to the affairs of his dis­integrating country, into shooting a series of anthologisably bad feature films.

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In October last year, in what turned out to be the last fortnight of Sihanouk’s life, my father and I returned to Phnom Penh for the first time since our ejection nearly half a century ago. At a retrospective of the prince’s work at the Bophana Centre, a superb audiovisual and visual archive founded by a technician who had worked on the movies, we watched perhaps the most representative of Sihanouk’s nine films, La Forêt Enchantée. It is dedicated to the memory of Kantha Bopha. A print had been discovered in the street after the collapse of the Khmer Rouge regime in 1979, following Cambodia’s invasion by the North Vietnamese, and sent back to Paris to be digitised. An orgy of nepotism, in which Sihanouk assumed the roles of director, producer, librettist, screenwriter, set designer and principal actor, La Forêt Enchantée cast contemporary Cambodia as a fairy-tale forest kingdom and starred Sihanouk’s wife Monique, his daughter Bopha Devi, a senior army general, and the prince himself as a mythical forest spirit.

Meanwhile, in another part of the forest, a Paris-educated Marxist, Pol Pot, was planning his revolution and showing Sihanouk’s films as propaganda. My father was educated in Paris at the same time as the Khmer leader and he recalled how Pol Pot’s movement was reported in its early days. “In his radio broadcasts, Sihanouk often appealed to his Khmer brothers in the jungle to come back, so we knew about these people. He would refer to them like members of a family who had gone astray, more in sorrow than in anger. “We thought they were a little band of renegades living in the remote forests. Perhaps that’s all they were then.”

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Many of those who see Sihanouk’s face in the moon believe that he brought peace to Cambodia: in 1991, after more than two decades of civil war, he buried the hatchet with a one-eyed Khmer Rouge battalion commander, Hun Sen, who had been the country’s de facto ruler since 1985, and still is. But in fact, a great many others see Sihanouk as largely to blame for the Khmer Rouge and also responsible for the movement acquiring that name. After Lon Nol deposed him in 1970, a hysterical and hurt Sihanouk urged his loyal subjects to flee into the same forest as Pol Pot, broadcasting to the people from Beijing on 23 March: “Brothers and sisters, go to the jungle and join the guerrillas.”

Before that critical moment, as a former Khmer Rouge fighter told me: “We did not have even a section.” Sihanouk’s sanction opened the door for Pol Pot and his deranged regime to “govern” Cambodia between 1975 and 1979. Along the way, they put to death a third of the population. Among the 1.8 million casualties was our gardener Hem.

In the past year, four of the Khmer Rouge leaders have been on trial in Phnom Penh for genocide, war crimes and crimes against humanity. They included Ieng Thirith, the bespectacled, 80-year-old former minister of social affairs and sister-in-law of Pol Pot. In the early 1950s, when my father was a lecturer at the École Normale in Paris, she was studying Shakespeare at the Sorbonne and translating his plays into Khmer. Just before we flew back to Phnom Penh, she was released from detention – on account of Alzheimer’s. Her English lawyer told me that the UN-backed tribunal’s Cambodian judges initially had difficulty grasping the idea of Alzheimer’s disease. “They didn’t understand it because, my theory is, Cambodians didn’t live long enough.” Thirith was among the few people in her country who had grown old enough to be in the fortunate position of not remembering what she had done.

So far, the only person who has been convicted for atrocities that occurred during the Khmer Rouge years is a giggling former mathematics teacher known as Duch, who ran the Tuol Sleng torture centre at a former lycée in south Phnom Penh. Eradicating all evidence of bourgeois individualism, Duch the mathematician and his regime replaced the names of people, streets and institutions with numbers: Tuol Sleng became S-21. Duch would examine prisoners’ palms and be surprised to find those who had a long lifeline. “It’s not true!” he would say. Afterwards, he would have the prisoners executed – 12,380 of them in total. “Usually we slit their throats. We killed them like chickens.”

Some were subjected to medical experiments. One of those Duch dissected alive was the wife of Lon Nol’s minister of education. He also ordered the executions of his primary school teacher (after she had been tortured with a stick in her vagina) and his own brother-in-law. “Whoever was arrested must die, it was the rule of our party. Even children. No one could leave S-21 alive.” In February last year, he was sentenced to life imprisonment by the war crimes tribunal.

One rainy morning, we visited Tuol Sleng, where children were dropped from balconies. “They were killed to prevent them from being a nuisance,” said a guard, Prak Kahn. Before the prisoners were killed, they were photographed. Their faces gaze out from a wall in what is now a holocaust museum, beneath a sign forbidding visitors to laugh.

These children were the age I was when I lived in Phnom Penh and took my first history lessons at the Lycée Descartes, sitting in a classroom, possibly at the same slanted wooden desk, where several pupils who grew up to become leading members of the Khmer Rouge had sat.

Suddenly each face was looking at me, staring out over dark collars in the way only children can do, in the way that Kantha Bopha may have gazed at Sihanouk, in chastising innocence and bewilderment, as if saying: “Why did you leave us to die?”

Seated outside in the courtyard behind a table piled with histories of this period was one of only two living survivors of S-21. Chum Mey was a small husk of a man who has recited his story almost daily since 1989. I asked him to show me his former ground-floor cell in the building behind. He led the way across the rain-spattered tarmac – from the back, a clerk or an accountant; fine white hair, buttoned yellow shirt, watery brown eyes drained of expression – and into a classroom with a floor of the original orange and cream tiles, on the wall the remnants of a slogan (“If we join together we will be stronger”).

The room was divided down the middle by two rows of crude brick cells. Number 22 was one metre wide, two metres long, and identical to every other. Chum Mey pointed at the metal bullet case on the floor – his toilet. He could not talk to others in the cells, though he heard their cries. He could not look out of the window, now open, into the courtyard planted with frangipani trees. “I could not see the leaf of a tree or a bird.” A smile blurred his face. When it subsided, it left all that had sunk to the bottom poking up.

Chum Mey was interrogated and tortured for 12 days, obliged to confess that he worked for the KGB or the CIA, even though he never knew what the names meant. If he complained or made a noise or moaned, he was taken out to the interrogation room and tortured again. He showed me his hands, the fingers broken, then stooped down to his feet to indicate the toenails that had been ripped out (in some cases the mashed hands or toes were plunged into buckets of urine). Then he pointed to his ears, into which Duch’s men inserted an electric wire, and he said, “Buk, buk,” and his body shook and his eyes rolled white and he tapped his forehead in a gesture to indicate that he blanked out. But he was glad the Europeans were making the UN tribunal happen, because at last he could speak openly after many years when he couldn’t. His wife was shot dead with their newly born son in the final days, as he ran to escape from S-21 guards and found her on National Road 4. Her last words to him were: “Run, baby! They’re going to shoot me.”

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One evening my father and I had dinner beside the Tonlé Sap, the only river in the world that completely changes direction, twice each year. Punctual as blossom at the end of the rainy season in November, the grey waters start flowing the other way – rather like the shifting political views of Sihanouk and his successors.

What it shocked us to discover was that some of the same people who out of extreme Maoist views abolished currency and schools and expelled Phnom Penh’s population, including our gardener, into the countryside were the ones still in power under Hun Sen; and that they continue to drive Cambodians from their land, only now in the name of no ideology other than profit. The bulk of Sihanouk’s enchanted forest – the priceless rosewoods and yellow vine – had been logged and flogged. And not only the forests: a young Cambodian working for Oxfam told us that, since 1998, when the Khmer Rouge finally laid down their arms, 700,000 people had been dispossessed and 63 per cent of the arable land sold off to private companies, many of them owned by Cambodia’s old enemies, the Thais and the Vietnamese.

“My country,” he said, “is like an old and dilapidated house, newly painted on the outside – but go inside and you see it’s going to break down very soon. Democracy is only a shadow, a black shadow.”

I spent two days visiting the shacks of Cambodians forcibly thrown out of Phnom Penh to make way for shopping malls on land suddenly claimed by Hun Sen and his cronies. Senator Lao Meng Khin, for instance, purchased Boeung Kak, the biggest lake in Phnom Penh, and the land around it without public consultation or access to information about the lease or what he paid for it (a rumoured $79m). Four thousand, two hundred and seventy families had been removed from around the now filled-in lake. When they protested, 15 women were arrested and imprisoned. One of the women showed me an effigy that she created to represent Hun Sen and his government, the figure dressed as Pol Pot but with dollars spewing from his straw head. She said with contempt: “They take our land, they evict us, they lose us our livelihoods, they put us in jail. They are the same as Pol Pot, but they need the money.”

In June 2006, another 1,367 families were uprooted and dumped in an open field in Andong, 22 kilometres away. They had received “not one grain of rice” in compensation. The government was yet to provide electricity, medical facilities, sanitation. “You see that field?” said an old lady, and angrily pointed her finger. “That’s everyone’s toilet.”

If Andong painted a pestilential picture of what happens to people who are uprooted from their native soil, the village of KrangLa Hong offered a grain of hope. Thanks to NGOs such as Oxfam and Licadho, the village chief had learned his legal and human rights, and how to mobilise his community. When a quarrying company laid claim to the local forest and came one night with armed men to cut down the trees, Nhann Kong and 50 villagers confronted the bulldozers and demanded to see a valid document. Not only did Kong save his forest, but he introduced rice-growing practices that, in three years, revolutionised conditions in his village and six others besides. By planting rice shoots singly instead of clumps of ten – the habit in Cambodia for at least a thousand years – Nhann Kong increased his yield twofold.

His family no longer goes hungry for three months of the year, and he can sell the surplus. Standing in his kitchen beneath a surprisingly bright light – fuelled, like his gas ring, by manure from his cow – he told me how, with the money from his rice, he had been able to buy concrete for his house, a motorbike, and education for his children.

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At the end of our visit we returned to Angkor. We had stopped off briefly on our flight to the border. Lying in the heart of Sihanouk’s enchanted forest, the 10th- to 13th-century temple complex provided his most extravagant film set. He was not alone in drawing inspiration from the ruthless Khmer rulers who built it – at who knows what human cost. Pol Pot and Hun Sen, too, invoked them.

Angkor was both impressive and unsettling. Visiting in the 1920s, the French poet-diplomat Paul Claudel found it “one of the most accursed . . . evil places that I know”. As we wandered again along the Terrace of the Leper King, I thought of the words of an exasperated forestry expert who since 1996 has monitored the government’s involvement with illegal logging: “The problem with the Khmer Rouge was not the ‘Rouge’.” Ever-changing and all-promising, Norodom Sihanouk incarnated the spirit of his great Khmer forebears.

In the final week of his life, on our last morning in Cambodia, I climbed with my father up the steep steps of the Bayon Temple, where the gigantic face of a divine ruler is carved into all four sides of each tower. It stares out in every direction, as if broadcasting the line that Sihanouk said about himself, best read to a tune by Édith Piaf. “I’ve experienced everything, won everything, lost everything, I’ve seen wrong, seen everything too soon, I didn’t see the dagger in my back, I’ve made mistakes, I have often lied, I told the truth a lot, too much.”

Nicholas Shakespeare’s most recent novel is “Inheritance” (Vintage, £7.99)