Saudi Arabia is planning a three-way stock market listing for state owned Saudi Aramco. The oil giant will list shares in London, Hong Kong, and New York. Aramco is the biggest oil company in the world, overshadowing ExxonMobil, the largest publicly traded oil and gas company. Aramco will sell 5% of its equity, valuing the shares at approximately US$125 billion (£87.5 billion), according to Prince Mohammad bin Salman, the favoured son of King Salman who has established himself as the effective ruler of the Kingdom. Its record-breaking stock market listing is expected to value the company at $2.5 trillion and is scheduled for either next year or 2018. In comparison, ExxonMobil's market capitalization is approximately US$370 billion.

Aramco is the largest oil company in the world, controlling around 10% of the world's oil output and also the largest holder of proven reserves.

The Saudis are reportedly trying to convince international oil giants ExxonMobil, China's Sinopec, and BP to take strategic stakes in the listing, offering them long-term access to upstream operations in exchange.

The proceeds of the sale will be invested in diversifying Saudi Arabia away from oil, as part of the country's Vision 2030. The person calling the shots is 30-year-old Deputy Crown Prince Mohammed bin Salman, who has established himself as the effective ruler of the Kingdom. King Salman is technically the ruler, but Prince Mohammed is increasingly calling the shots on some pretty important events.

And his power over one of the world's most important economies was made abundantly clear recently when he replaced 20-year veteran oil minister Ali al-Naimi with someone who he directly controls the actions of — Khalid al-Falih, chairman of Saudi Aramco.