Last Saturday night a young Arab prince took a shower in his marble bathroom, chose a multicoloured Versace shirt from his walk-in wardrobe, put on slightly too much cologne and drove a rented Ferrari to a nearby club. As his social life revolves around what are known in his world as “the Three Bs”, he could tell what country he was in by the sign above the nightclub door: B Club means Geneva. If it had read Bungalow 8 he would have been in New York, Boujis in London.

Whatever the city — and he and his type know many — the routine is always the same. A line of locals queue round the block but diplomatic immunity causes the velvet rope to snap open for him. Inside there is dancing, drugs, girls, and plenty more. Cristal champagne comes at £330 a bottle. At 4am by his Oyster Rolex, our prince headed home with a beautiful Russian who might or might not be a prostitute.

This is the world of the children of Arab sheikhs and African dictators, and, judging by last week’s reports, it is a scene that Kojo Annan is familiar with. The son of Kofi Annan, the UN secretary-general, grew up on the international circuit and is a member of an international brat pack “The Sons of . . .” Educated in Switzerland and Britain, his friends include the son of the former Nigerian dictator General Sani Abacha, and Hani Yamani, the son of Sheikh Yamani, the former Saudi oil minister.

One acquaintance of Kojo remembers him on a February day in London, cosseted in the back of a chauffeur-driven Mercedes, wearing a black polo neck and sporting sunglasses despite the winter gloom.

Last week was a less relaxing one for Kojo, who is said to fancy himself as an international man of business: the findings of an independent inquiry into the oil for food scandal and his consultancy with the Swiss company Cotecna Inspection. The report accused him of having “actively participated” in efforts to hide the nature of his involvement with the firm. His loyal father, Kofi, spoke up for him: “I love my son,” he said.

So what is life like as a “diplobrat”? The daughter of a high-ranking diplomat says that “as UN kids we were exposed to everything, and I mean everything. Though you can’t live like the royalty you meet on a UN salary, opportunities and temptation are everywhere”.

Thant Myint-U, a UN political officer and grandson of former UN secretary-general U Thant, says the days of excess have gone — “UN salaries have suffered a huge relative decline compared with those enjoyed by American businessmen” — but his childhood memories include “garden parties with people such as Prince Sadruddin Aga Khan” and meeting Neil Armstrong on his return from the moon.

Kojo was born in Geneva to his father’s first wife, Titi Alakija. When the couple divorced, Alakija took Kojo and his sister Ama to live in Lagos, Nigeria, before returning to Geneva so Kojo could attend the exclusive private school La Chataigneraie. Perched on a hill overlooking the lake, the school’s chateau has one of the best alpine views in town. The student body is similarly magnificent. “There weren’t any dictators’ kids in my year,” one former student recalls, “but we had a few Greek shipping magnates and the odd UN agency head.”

Matt Wilmer remembers life in a private school nearby, studying alongside members of the Gadaffi and Hussein (as in Saddam) households: “It was a very different kind of childhood. During the first Gulf war they put guards all around the perimeter but the real problem was inside. The Iraqi and Kuwaiti kids were always kicking off in the playground so it was like we had our own little Gulf war.”

For the children of modestly paid, mostly middle-class UN staffers, a backdrop of international politics can provide for a high-octane upbringing. Nick Greenstock, son of Sir Jeremy Greenstock, a British diplomat and former ambassador to the UN says: “As the son of a diplomat you have to be careful. You sit at the same table as some very powerful people.”

“It takes a lot of willpower not to dip your toe into that world from time to time,” says Wilmer, who sees cities such as Geneva as pleasure parks when you’re young and well connected. Prostitution is legal in Geneva and apparently it is not uncommon to see the sons of some of the world’s ruling dynasties picking up street walkers on their Saturday afternoons: “Money was never an issue with that crowd. They definitely had more money than morals.”

“The sheer opulence of it was overwhelming sometimes,” says Kimberley Sachs, another student at the school. “Boys would come to school with £20,000 Patek Philippe watches. I even heard about one group of guys who ended up at an auction in Gstaad after a serious bender. They came home in an antique Rolls-Royce that the son of a nuclear fuel magnate had bought on a whim.”