In England, the North Korean Embassy operates out of a nondescript, semidetached house in the suburbs of west London, far from the diplomatic hubbub. In France, the pariah state responsible for a litany of human rights abuses is far less visible, in that is has no official diplomatic representation at all. The same goes for the United States.

But here in Cambodia, the North Korean ambassador wakes up next-door to Prime Minister Hun Sen in a mansion that belonged to the royal family for three generations.

There’s another perk, according to several people familiar with the property: It’s rent-free.

A gift from the late King Father Norodom Sihanouk, the embassy – his birthplace – was leased at no cost to North Korea in 1991 for a fixed period of 20 years, after which it was to become a museum. That agreement, which was reiterated in Sihanouk’s 2005 will, technically expired in 2011. Savvy tenants, the North Koreans haven’t moved out.

“King Sihanouk gave the house for 20 years rent-free to the DPRK [Democratic Republic of North Korea] to express his gratitude for the assistance the founder of the DPRK, president Kim Il Sung, gave to the late King, particularly during his years in exile between 1970-1975 and again [in] 1979-1991,” said Julio Jeldres, official biographer for Sihanouk, who died in 2012.

The embassy continues to occupy the two-storey house on Suramarit Boulevard, where it has allegedly harboured Japanese Red Army terrorists, aided a multimillion-dollar money-laundering operation and served as a source of anxiety for the government.

Representatives of the royal family say it is time the house is returned and becomes what Sihanouk ordered in his will: a museum belonging to Cambodia filled with pre-Angkorian and Angkorian-era artefacts.

“As far as I’m concerned, it’s up to the government to negotiate with North Korea,” said Prince Sisowath Thomico, Sihanouk’s nephew and former aide. “It should have been handed over to Cambodia. It was his wish.”

Built during the French Protectorate by Sihanouk’s grandfather, Sisowath Monivong, the house was given the name Teaksin Phirom. Monivong later handed it down to his favourite daughter, the then-Princess Sisowath Kossomak, who raised her son, Sihanouk, there.

They lived in the house until the early 1940s, when Sihanouk moved to the Royal Palace.

After the 1970 coup and proclamation of the Khmer Republic, Kossomak returned to Teaksin Phirom. It was the last place she lived. But less than 20 years after her death, her son signed it over to North Korea’s iron-fisted ruler, Kim Il-sung. The man responsible for the deaths of hundreds of thousands proved a loyal friend to Sihanouk, and Sihanouk didn’t forget his friends.

“We called him the ‘great leader’,” recalled a source close to the palace who was not authorised to speak to the press. “Kim Il-sung addressed Sihanouk as ‘leader of the Cambodian people’.”

The pair had forged a close friendship over the decades following the fall of the Khmer Rouge, when Sihanouk – in exile in Beijing and Pyongyang – fronted a resistance to the Vietnamese-backed proxy government.

One of the words most commonly used of the relationship by those who knew them both is “unconditional”.

What united them, said the palace source, was a nationalistic sense of duty: “At first, it’s the idea of the two of them serving the nation. They both think what they are doing is for the nation.”

Kim gave Sihanouk a 60-room mansion close to Pyongyang named Jangsuwon, which stood on a hill overlooking a manmade lake. He shot several of his films on the grounds. His family took boat trips there, played badminton and swam in the pool.

Much like the gift of the house, the relationship survived.

“Kim Jong-il respected the King as much if not more than Kim Il-sung,” said the palace source, referring to Il-sung’s son, the father of the current leader, Kim Jong-un. “Kim Il-sung was as an equal – the son respected the King even more.”

When Sihanouk returned to Phnom Penh in 1991, a retainer of North Korean bodyguards in tow, he signed Teaksin Phirom over to his old friend.

“During the years of 1979 until 1991, the country which helped Sihanouk most on a personal level was Kim Il-sung’s North Korea, so as a gesture of gratitude, King Sihanouk decided to lend his home to North Korea,” Thomico said.

But in the years that followed, the embassy was known more for its scandals than its history. In March of 1996, the mission was found to be harbouring Japanese Red Army militant Yoshimi Tanaka, who, among other misdeeds, hijacked a commercial airliner and was accused of laundering more than $3 million in counterfeit $100 bills. He was promptly arrested in Phnom Penh.

Sheena Chestnut Greitens, a senior fellow with the Center for East Asia Policy Studies at the Brookings Institution, said that “embassies and diplomats played a central role in the first phase of North Korean involvement in criminal activity, which began in the 1970s, including in the distribution of counterfeit currency”.

In a diplomatic cable sent in 2006, Om Yentieng, personal adviser to Prime Minister Hun Sen, registered concern about the proximity of their embassy to the premier’s house, lest Cambodia’s cooperation with South Korea over refugees from the North become public knowledge.

The relationship between Cambodia and North Korea lost steam, and in July of 2005, Sihanouk made clear his intentions for the house with a signed will that said Teaksin Phirom should become a museum once the lease was up.

Jeldres said that the late King Father specified in his will that the mansion should house pre-Angkorian sculptures currently held at the Conservation D’Angkor, a makeshift storage space in Siem Reap.

“In the said will, his late Majesty also requested that the royal government take care of the up-keeping of the museum and ‘never demolish or sell the Teaksin Phirom’ as well as preserve it forever.”

The reason why the hermit kingdom continues to retain Sihanouk’s house is unclear, though some members of the royal family remain friendly with North Korea.

According to the palace source, Queen Norodom Monineath prays to a bronze statue of Sihanouk made in Pyongyang.

“Very close, still very close with the Queen Mother,” said Thomico. “Each year, on the Queen Mother’s birthday, the ambassador would come and pay his respects to the King and the Queen Mother.

The relations are very friendly.”

A Phnom Penh-based diplomat attributed the lack of action to cash-strapped North Korea’s refusal to move out, and the “lack of budget at the Foreign Ministry” to provide a new building.

When asked about the embassy, Koy Kuong, spokesman for the Foreign Ministry, said he had “no information about that at all” and knew no one who did.

The North Korean embassy could not be reached for comment. A security guard at the entrance to the embassy shook his head vigorously in response to an in-person request from a Post reporter for an interview with the ambassador.

What goes on behind the tinted windows at the embassy remains a mystery.

Diplomatic sources say that while the ambassador attends events regularly, he tends to scurry away from Western nations’ representatives after he is introduced.

There’s no sign of Sihanouk’s museum, as North Korea quietly expands its footprint in the Kingdom, with four cash-generating restaurants in Phnom Penh, a fifth coming soon, and more already established in Siem Reap, where it has built a museum dedicated to Angkor Wat. .

Outside the house where Sihanouk was born, laminated photos and signs continue to laud the pariah state’s “dynamic advance” and its former leader, “Kim Jong-il, genius of ideology”.

There are no pictures of Sihanouk.