Continuity and stability have long been the watchwords for the ruling family of Saudi Arabia, and since 1953 and the succession of King Saud bin Abdulaziz, a half-brother of the present King, the succession of the monarchy has been passed to the sons of the kingdom’s founder, King Abdulaziz, providing 60 years of continuity.

So, while the passing of Saudi Arabia’s Crown Prince Sultan bin Abdulaziz al Saud after a long battle against cancer will not have come as a surprise to many people in the kingdom, it is an unwelcome reminder that the generation of men that has run the country for six decades is coming to an end. And no-one is sure what comes next.

King Abdullah is in his mid-80s, and the most likely person to be named as heir is Interior Minister Prince Nayef bin Abdulaziz, who was named second deputy prime minister in March 2009, and who is in his late seventies. Riyadh governor Prince Salman bin Abdulaziz, who many believe will follow Nayef, is of a similar age.

From the outset, King Abdullah has focused on the need for a smooth succession as the sons of King Abdulaziz enter their final years. In 2006, he created of the Allegiance Council – known as Al-Hayaat al-Bayaa in Arabic - the first significant Saudi response to the looming challenge of succession. Made up of the sons and grandsons of King Abdulaziz, its mandate is to determine the eligibility of future generations of kings and heirs. The Allegiance Council represents an attempt to institutionalise a formal succession arrangement to smooth the transfer of power between generations.

There have been other changes to ensure that future monarchs are fit for their role. For the first time, a ruling Saudi monarch is now subject to medical health checkups that could determine his suitability to continue as ruler. But perhaps more significantly, the prerogative of a reigning monarch to appoint his successor has been handed over to the committee to decide.

Naturally, the identity of future monarchs is still subject to intense debate and speculation. Of the 20 surviving sons of King Abdulaziz alive today, one of the youngest – and increasingly cited as a future king – is General Intelligence Directorate (GID) chief, Prince Muqrin bin Abdulaziz, who is 65.

With Prince Sultan’s death comes the uncomfortable question of how the country’s leadership will pass to the next generation, Ibn Saud’s grandsons. And, more specifically, whether the many tensions that exist within the country’s enormous ruling family will lead to an internal power struggle creating a period of political and economic uncertainty in the kingdom, and beyond.

However, the issue cannot be delayed indefinitely, and at some point, Riyadh must make a decision about which branch of the Abdulaziz sons will follow. The problem for the kingdom, as it seeks to preserve continuity and stability, is that whatever decision it takes, it will cause controversy.

The passing of Prince Sultan however highlights how pressing the issue has become.