To understand why Saudi Arabia changed course and decided Opec should go back to managing supply, look at two of the kingdom’s biggest policy challenges: The urgent need to plug holes in its budget and the plan to sell a stake in the state-owned oil monopoly.

NOT even Pádraig Harrington, widely regarded along with Vijay Singh as the hardest worker in the game, has been able to get in some practice since the cold spell kicked in just before Christmas.