Saudi Crown Prince Sultan bin Abdulaziz al Saud - the 15th son of Saudi Arabia’s founder - died yesterday, aged 80.

The crown prince, who was first in line to the throne, was also central to Saudi Arabia’s relations with Western countries.

He was The Kingdom’s powerful defense and aviation minister since 1962. In that role he orchestrated enormous arms purchases from the U.S., U.K. and France that turned Saudi Arabia into one of the largest importers of defense equipment in the world and an important military ally for the West.

Prince Sultan was diagnosed with colon cancer in 2004. It is thought that he had been in the US where he was receiving medical treatment when he died in a New York hospital.

A state funeral is planned for Tuesday in Riyadh, according to the official Saudi Press Agency.

Saudi rulers are expected to move quickly to name the new king-in-waiting — is thought to be the Sultan’s half brother, Prince Nayef - according to royal protocal.

He is survived by 32 children from multiple wives. They include Bandar, the former ambassador to the United States who now heads the National Security Council, and Khaled, Sultan’s assistant in the Defence Ministry.

Britain’s foreign secretary, William Hague, said Sultan served his country with “great dignity and dedication.”