The Arab world held its breath last night as Jordan's King Hussein flew home to die from lymphatic cancer. Although the new Crown Prince Abdullah has performed well so far and is being courted by Arab rulers, no one believes he was destined to succeed his father.
That role had been either assigned to King Hussein's younger brother, Prince Hassan, who served as crown prince for 34 years or preserved for Prince Hamzah, the king's fourth son, who was groomed for the job.
For the region the passing of King Hussein, who has ruled for 46 1/2 turbulent years, will be a brutal blow.
King Hussein is the foremost Arab statesman, honoured by friends and respected by antagonists. Without him Jordan, in the throes of economic collapse and beset by political contestation, could become destabilised.
Without him the Arab world has no ruler capable of appealing to both ordinary Arabs and influential Western leaders. If the king's untutored, untried heir fails to meet challenges which arise, this could mean the fall of the Hashemites, who trace their lineage to the family of the Prophet Muhammad.
For the Arabs, as a nation if not all citizens of the same country, this would amount to a historic disaster because the Hashemites represent Muslim Arab legitimacy at a time few Arab regimes have either legitimacy or credibility.
In the absence of Iraq, the core country of the eastern Arab world, isolated by the international community and impoverished by sanctions, instability in Jordan could ripple through the region.
The first Arab leader to fear the removal of King Hussein is the Palestinian President, Mr Yasser Arafat, another elderly autocrat in poor health.
Although the two men are old antagonists, they have reached a modus vivendi whereby Mr Arafat took over responsibility for the Palestinians of the West Bank - whom King Hussein ruled until June 1967 - and the king accepted as full Jordanians the two million-plus Palestinians who dwell in his kingdom. And the Palestinians have accepted the king.
But Palestinian acceptance of the Hashemites may not extend to Abdullah. Although Abdullah has a Palestinian wife, he has made his career in the army which, in 1970, crushed a Palestinian insurrection, creating decades of hostility between the Hashemites and their Palestinian subjects.
Instability in Jordan could produce problems for Israel. Over the past 50 years the Jewish state has counted on the Hashemites to maintain a strong, centralised security-conscious regime in Jordan.
Jordan's unpopular 1994 peace treaty with Israel was imposed by the king and could be revoked after him. This could undermine fragile relations between the Arabs and Israel and force Egypt to reconsider its 1979 treaty.
Syria, also ruled by an ageing, ailing autocrat, Mr Hafez alAssad, cannot but feel the impact of King Hussein's disappearance. Mr Assad's surviving son, Bashar, is being prepared for succession but, like Crown Prince Abdullah of Jordan, it is not clear that he will manage to take over from his masterly father.
Instability in Syria can only beget crisis in Lebanon which has not yet been properly prepared to assume its own internal security following the 1975-90 civil war.