Khalid’s father, Salem, was an illiterate money changer who would go on to become the founder of the first, and now the biggest, bank in Saudi Arabia, the National Commercial Bank of Saudi Arabia (NCB).

And when his son inherited the reigns (and a significant holding) two decades ago, he was to prove a canny operator, able to read the markets and anticipate the best moment at which to let stock go.

In 1997 he sold a 20.7 percent stake of NCB for $1.8bn to a group of private investors. In 1999 he sold a further 50 percent of the family’s holding to the Saudi Public Ownership Fund, and in late 2002 the family sold its remaining stake to the same fund.

Khalid poured the money into a Jeddah-based global investment group with his sons and retained significant holdings in various real estate development and other companies inside and outside Saudi Arabia, including Capital Investment Holdings of Bahrain. His umbrella of investments included an interest in Thuraya Satellite Telecommunications Company in the UAE.

He also invested in US-based satellite radio pioneer Worldspace, which filed for bankruptcy protection in the US in October in 2007 – a sharp but not significant blow to Khalid, who maintained opulent homes around the world and travelled in his own Boeing 767 with gold-plated bathroom fixtures.

Four years ago Mahfouz won a court battle to clear his name of any association with terrorism, when an English High Court Judgment found that author Rachel Ehrenfeld and publisher Bonus Books made defamatory statements about his family.

Mahfouz did acknowledge making one contribution to Al Qaeda. He donated $270,000 when the organisation was fighting the Soviets in Afghanistan. At the time, the US also supported the insurgents there.