Jordan is, relative to the turmoil of its region, a haven of stability, though the royal court of its Hashemite dynasty has at times been a jostle of intrigue. This is one of those times.

The late King Hussein, in his time the west’s gold standard of gracious Arab despotism, survived plots, coups, uprisings, three Arab-Israeli wars, two Gulf wars, a civil war with the Palestinians and around a dozen assassination attempts in his 46-year rule.

His son King Abdullah, on the throne since 1999, on Saturday placed Prince Hamzah, oldest son of Hussein’s fourth wife, the American-born Queen Noor, under house arrest. Amman says it has uncovered a plot threatening the “security and stability” of the country.

Up to 18 people have been arrested, including palace aides of Hamzah, who in 2004 was stripped of the position of crown prince when Abdullah made his first son, Hussein, heir apparent.

The two main detainees are Bassem Awadallah, once chief of King Abdullah’s court and a former finance minister, and Sharif Hassan bin Zaid, a minor royal. Awadallah was the king’s envoy to the Saudi court, where he became an adviser to Mohammed bin Salman, crown prince and de facto ruler. Bin Zaid was formerly Jordan’s ambassador to Saudi Arabia.

Ayman Safadi, Jordan’s foreign minister, said on Sunday the authorities had long been monitoring the plot and intercepted “communications with foreign parties over the right timing to destabilise Jordan”. Some Jordanian officials are dismissing Hamzah’s role, saying plotters used his “illusions and aspirations” to further their own interests.

This is not, on the face of it, a coup nipped in the bud. It was the army chief of staff who told Hamzah to cease his activity. The military and the Mukhabarat, the powerful intelligence service, are the bedrock of Hashemite rule, rooted in the East Bank or native Jordanian tribes, as opposed to the Palestinian majority driven across the Jordan river from the West Bank in the 1948 and 1967 Arab wars with Israel.

But Prince Hamzah is more than an illusionary figure. “He’s been swimming in murky waters for years,” says one confidant of the king.

Tutored for kingship from birth, he looks, speaks and dresses like his late father, and cultivates conservative tribal leaders, disaffected with Jordan’s struggling economy and joblessness, its corruption and patronage, and its increasingly unbenign despotism — everything Prince Hamzah denounced in defiant videos after being told to desist.

“I am not the person responsible for the breakdown in governance, the corruption and for the incompetence that has been prevalent in our governing structure for the last 15 to 20 years and has been getting worse,” Hamzah said.

Outsiders tend to focus on Jordan’s Palestinian demography as a security challenge but the Jordanian elite is wary of unrest in the East Bank tribes, the regime’s natural constituency. Indeed, it was then Prince Abdullah, commander of elite special forces, who put down bread riots across the loyalist south in 1996. That, and a court jostle between factions that included Hamzah, won Abdullah the throne.

“This is a family matter and they are dealing with it in a family way,” said foreign minister Safadi at the weekend. Prince Hamzah’s videos suggest otherwise but on Monday night he signed a public pledge of allegiance to the king.

King Abdullah is supported by the west and, ostensibly, by his western-allied neighbours. But there are visible strains with Israel and Saudi Arabia, which intersect over Jerusalem. There is suspicion in Jordan that the House of Saud wants to take oversight of the city’s Islamic sites from the Hashemites — from whom crown prince Mohammed’s grandfather took the holy cities of Mecca and Medina in 1925 — as the price of Saudi detente with Israel. There is more intrigue to come.