The man who may one day have his finger on the North Korean nuclear button was taught basketball by an Israeli and is a fan of Japanese cartoons and Arnold Schwarzenegger, aka the Terminator, a former schoolmate revealed yesterday.

Kim Jong Un, the son of the Dear Leader and grandson of the Great Leader, was a bright outgoing pupil when he entered his teenage years at the International School of Berne, according to the former fellow pupil.

Mystery surrounding the health of the North Korean dictator Kim Jong Il, who seems to have nominated his son as his political heir, has made the trivia of Mr Kim Jr’s schooldays interesting to intelligence services.

Will Kim Jong Un, 26, open up one of the most closed societies in the world? What are his views on non-bodybuilding Americans? And how itchy will that trigger finger be?

“He had a sense of humour; got on well with everyone, even those pupils who came from countries that were enemies of North Korea,” said the pupil, speaking anonymously to the German newspaper Welt am Sonntag. “Politics was a taboo subject at school . . . we would argue about football, not politics.”

Kim Jong Un was enrolled at the international school between 1993 and 1998 under the name Chol Pak. He was chauffeured to lessons every day — not unusual at a school whose pupils were drawn from diplomatic or rich Swiss families — and it was kept vague about whether he was the son of the chauffeur or of a senior envoy. He lived in the North Korean Embassy and would be seen in town eating with the Ambassador.

So far the main anecdotal information about Kim Jong Un has come from his father’s Japanese sushi chef, writing under the pen name Kenji Fujimoto. The chef worked in Kim Jong Il’s kitchens for 20 years and in his memoirs describes Kim Jong Un as pleasant, overweight, capable of holding his drink and a fan of the US basketball player Michael Jordan.

He learnt to play basketball at his Swiss school, even though he was on the short side — some reports say he is 5ft 6in.

“An Israeli pupil taught him the basketball moves,” the fellow pupil said, “and he spent a lot of time with a South Korean, I think because the South Korean could draw comic strips well and Chol Pak was a fan of the Japanese manga characters.”

Kim Jong Un’s mother, the former dancer Ko Yong Hi, was Japanese-born. She reportedly died of cancer in 2004 after Kim Jong Un had returned to Pyongyang.

Another North Korean pupil, Kwang Chung, joined the school at the same time as Chol Pak. It was suspected that he was Kim Jong Un’s bodyguard.

“Once he [Kwang] kicked a pencil out of the mouth of a pupil,” the former classmate said. “A normal child couldn’t have done that — he must have been trained in martial arts, perhaps a soldier who looked particularly young.

“Kwang . . . was more popular than Chol because he was so good at sports. They talked about Schwarzenegger films the whole time.”

The boy called Chol was good at maths — “but he wasn’t a nerd” — and he was involved in school charity projects.

“Probably the North Korean in him is stronger than his upbringing as a pupil of an international school, but sometimes I think: at least he has experienced Western culture in its best form,” the schoolfriend said.

Kim Jong Un went on to attend the North Korean military academy. He has two brothers who, according to South Korean intelligence, have been ruled out of the succession.

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