It was a vast sham, since the television channels and leading newspapers had known about the engagement for weeks. And yet because of the peculiar role of the media in Japan, everyone co-operated in the make-believe theatre of the happy moment, declaring with one voice how overjoyed they were at the unexpected news.
The fact that this pretence could be maintained gives an interesting insight into Japan, and the legendary distinction between tatemae, or outward appearance, and honne, the underlying truth which is rarely articulated and is usually divined by subtle guesswork. For the television newscasters there seemed nothing incongruous in their upbeat tones as they relayed the surprise announcement, and the fact that within minutes of the news breaking they were all showing lengthy documentaries on the Crown Prince and his future bride, Masako Owada, which had clearly been prepared weeks beforehand.
The story starts a year ago, when the Imperial Household Agency, a tradition-bound institution which tightly controls all news about the Imperial family, asked the Japanese media to stop its hysterical coverage of potential brides for the Crown Prince. Some women had been hounded day and night by journalists, and the agency was afraid the press would interfere with the search for a future empress. So journalists collectively agreed to practice jishuku, or self-restraint, in their coverage.
The last time the press exercised this jishuku was in 1988, during the final protracted illness of Emperor Hirohito. The press respectfully reported on the amount of blood the emperor received in transfusions each day, but never once used the dreaded word cancer to describe his condition.
The period of voluntary self- restraint over Prince Naruhito's courting was due to expire at the end of this month, by which time a formal announcement was to be made. The Crown Prince, it now emerges, had already clinched his engagement with Ms Owada last month, and news organisations were discreetly told to prepare for the official announcement some time in January.
But news of this was leaked to a correspondent of a US paper stationed in Tokyo, who duly filed a story. Within minutes of the story appearing in the US, the news was back in Tokyo, and an emergency meeting of the Japan Newspaper and Publishers and Editors Association was called. It decided that the 'self- restraint' policy could no longer be maintained. Half-an-hour after this meeting, television stations simultaneously broke the story, while newspapers published special evening editions.
Foreign pressure had forced yet another change on Japan. In fact, the same thing happened in 1958, when foreign media were the first with news of the engagement of Akihito, the current Emperor, to his wife, Michiko.
Foreign reporters are excluded from the press club which covers the Imperial Palace, and therefore the foreign media were never asked to practise the self-restraint of their Japanese colleagues. Presumably the Imperial Household Agency did not think that foreign reporters would manage to ferret out the secret.
But far from being embarrassed about being scooped by a foreign paper on the Crown Prince's engagement, the Japanese press proceeded to congratulate itself on keeping the story quiet for so long. The day after the announcement, the Yomiuri Shimbun, Tokyo's most influential daily paper, said proudly that its editors had known about the engagement as far back as 12 December.
The contrast with the British press could not be more stark. It is hard to imagine an English paper running a story saying that a royal scoop published by one of its competitors had actually been known to its own reporters for four weeks, but kept quiet 'to protect the royal family's privacy'. But then the whole concept of voluntary self-restraint might be a bit difficult to explain to London's royal press corps.