By Frank Gardner
BBC security correspondent
On the surface, the transition from one Saudi king to another has been smooth.
Militant attacks have rocked Saudi Arabia in recent years
The succession had long ago been settled in private by a family counsel of 18 senior princes from the ruling al-Saud family.
But new king, Crown Prince Abdullah bin Abdul Aziz faces a number of major challenges that will affect the West.
The most visible of these is al-Qaeda linked terrorism, but others include creating jobs and dealing with the Israel-Palestinian and Iraqi conflicts.
For more than two years now Saudi Arabia has been battling a small number of well-armed militants.
They are intent on driving out Westerners and replacing the al-Sauds with an Islamic caliphate.
This week it has emerged that phone calls were made to Saudi Arabia by some of those suspected of involvement in last month's London bomb plots.
Crown Prince Abdullah is expected to continue his government's crackdown on the militants.
But he now has the full authority to also tackle corruption and extravagance in the royal family - an unpopular move with some princes, but one seen as essential to reforming this highly traditional kingdom.
Other pressing problems for the new king include creating jobs for thousands of restless school leavers, resolving the conflict in neighbouring Iraq and finding a solution to the Palestinian-Israeli problem.
The success or failure of Crown Prince Abdullah's reign matters to Britain.
Over 20,000 Britons live and work in Saudi Arabia.
It is a huge commercial and strategic partner and the continued flow of its oil to the west is vital to the global economy.