A plump Asian man in a pinstriped suit was caught on video the other week walking into the Sainte Anne hospital in a leafy street in Paris. He was Kim Jong-nam, eldest son of the ailing dictator of North Korea.

Two days later the elegant figure of Professor François-Xavier Roux, 57, chief neurosurgeon at Sainte Anne, was filmed at Charles de Gaulle airport boarding a flight to Beijing and thence, it is suspected, to the bedside of Kim Jong-il in Pyongyang.

The cameras were those of the Japanese station Fuji TV, tipped off to the secret comings and goings by furious officials in Tokyo. They think that the United States has betrayed its closest ally in Asia by taking North Korea off its list of terrorist states in a cynical attempt to broker a nuclear disarmament deal.

Traced by a French magazine, Xavier-Roux, who is a specialist in treating strokes and brain tumours with laser therapy, denied that he had been to North Korea. He is a close friend of Bernard Kouchner, the founder of Médecins Sans Frontières and now France’s foreign minister. The Quai d’Orsay, naturally, denied any knowledge of his trip.

The plot thickened. Japan’s prime minister, Taro Aso, a right-wing hawk, told a parliamentary committee that Kim, 66, is in poor condition in hospital but appears to be in command of his faculties and his country. Such a statement by a head of government is more authoritative than any media speculation and it infuriated the hermetic North Korean regime.

A stream of intelligence leaks from South Korea, where conservatives took over the government this year, painted a similar picture of a sick despot, a troubled elite and a dynasty paralysed by a succession dilemma.

Kim Sung-ho, South Korea’s intelligence chief, confirmed to a closed-door session of parliament that the man in Paris was indeed Kim’s eldest son and said that his father, although ill, appeared to be in control.

Foreign governments now generally accept that the “Dear Leader”, whose exploits are hailed as immortal, suffered a stroke in August. He has failed to appear at important events even though the state media have issued photographs showing him to be in apparent good health. However, these photographs were seemingly taken in the springtime.

Enraged by the publicity – and driven to distraction by South Korean activists raining leaflets on the North describing these events – the North Koreans threatened war last week.

Japanese militarists, claimed Rodong Sinmun, the ruling party newspaper, were plotting a preemptive strike against the country and will be repulsed in fire and blood.

The recent disclosures revealed that both Japan and South Korea keep the North Koreans under intense surveillance and also sent a hostile signal to Pyongyang’s cloistered elite. The two governments believe privately that Christopher Hill, the US negotiator, mistakenly appeased the North Koreans for the sake of a nuclear weapons deal that the regime has no intention of abiding by.

In Pyongyang mystery reigns over the succession. Kim Jong-nam, the eldest son who was entrusted with the delicate mission to Paris, would be the prime candidate under Confucian traditions of inheritance.

Exile websites, however, report that Kim Jong-chol, the second eldest son, is a rising force in the Ministry of the People’s Armed Forces, where he has acquired a reputation for being arrogant and headstrong.

The National Defence Commission, at present chaired by their father, is already functioning as a collective leadership and one or other son could be picked as a figurehead after Kim’s death.

Meanwhile, on a chill morning in Pyongyang the elite turned out last Thursday for the funeral of Pak Song-chol, a revolutionary veteran who died at 95.

Protocol determined that Kim should attend but instead the dictator sent a wreath.

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