In an open letter to Saudi ministers posted via Twitter, Prince Alwaleed bin Talal al-Saud expressed his “astonishment” at comments made by Ali al-Naimi, the oil minister, who reportedly played down the impact of oil prices falling below $100 a barrel. Prices have since fallen below $88 a barrel, or a quarter since June. Prince Alwaleed, noting the kingdom’s 2014 budget was 90 per cent dependent on oil revenues, said belittling the impact of lower prices was a “catastrophe that cannot go unmentioned”.