The mother and child are reported to be healthy and in good spirits. The happiness of the well-wishers outside the Imperial Palace was unfeigned, and the pregnancy even brought about a huge spike in the share price of manufacturers of baby-related goods.

But for one reason, and one reason only, the birth of a baby boy to Prince Akishino and Princess Kiko today was a disappointment — the fact that the 2.6kg, 49cm baby boy turned out to be a boy in the first place.

Japan was on the verge of a huge symbolic change — the change, after centuries of male succession, to a system in which a female member of the imperial family could reign as an empress.

The country’s outgoing Prime Minister, Junichiro Koizumi, was in favour of it. A government-appointed panel of eminent persons had presented in detail their reasons for supporting the reform. Public support for the move was as high as 80 per cent, and opposition was limited to a minority of — admittedly vocal — traditionalists and right-wingers. But today, thanks to an accident of chromosomes, the noisy minority won.

The question of revising Japan’s succession law will be shelved, perhaps for as long as a generation. Japanese men will continue to be the only permitted occupants of the throne.

In traditional fashion, female members of the imperial family will continue to walk, bow, stand and sit a beat behind their husbands, brothers and fathers. And the silent example which this sets at the apex of the Japanese state will continue to impair the equal treatment of women in the world’s second richest country.

Japan is a country where change comes gradually, often reluctantly and often when there is simply no other choice. By the mid-19th century it had become obvious that closed, feudal Japan was going to have to open itself to the outside world — but it took the gun ships of the American Commodore Perry to force it to happen.

Late in 1944 it was inevitable that Japan’s incompetent militarist Government was heading for defeat — but surrender only came in August 1945, after the atomic bombings and the entry into the Second World War of the Soviet Union. And so it is that a change in the succession laws, which most Japanese and their leaders wanted, was only going to happen as the result of a crisis.

By the beginning of this year, the crisis was in full spate. Since Prince Akishino was born almost 40 years ago, nine babies have been born into the Imperial Family. All of them have been girls.

The last was Aiko, the daughter of Crown Prince Naruhito and Princess Masako, who was conceived with difficulty after fertility treatment. Masako suffered a nervous breakdown three years ago — a situation which cannot have been made any easier by the intense silent pressure she faced to deliver a boy, rather than a mere girl.

Prince Akishino’s two children were both girls and, at the age of 39, his wife, Kiko, gave no sign of planning another child. Unless something changed the Imperial line was facing extinction, 2,700 years after its legendary beginnings in descendants of the Sun Goddess, Amaterasu Omikami.

Hence the panel of distinguished persons who spent a year considering the pros and cons and delivered their report and recommendations in November 2005.

The law, they said, should be changed so that the line of succession was determined by order of birth, not privilege of gender. On top of this, princesses should no longer lose their imperial status when they marry commoners — by remaining princesses they would thus be able to enlarge the reservoir of potential heirs.

The proposals were to be put before Japan’s parliament, the Diet, where they would have passed into law — and then, in February, news of Kiko’s pregnancy leaked out.

Courtiers insist that the couple had always wanted another child, and that right up until this morning they had no idea if it was a girl or boy. There is no proof that they were fibbing, but many Japanese assume the timing of the conception, and the gender of the baby, are too convenient to be a coincidence.

The irony is that today’s birth will only postpone the crisis. Unless the still-unnamed baby prince has a litter of sons of his own early in life, the imperial family will remain chronically short of heirs — imperial courtiers are working on the assumption that the succession law will have to be changed eventually.

There is no doubt that Kiko’s little boy will be the pride of his family, and an object of affection and interest for many Japanese. Too bad that his birth should also represent such a wasted opportunity.

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