Oil crash: why Saudi Arabia has started a global crude price war

The aggressive move by world’s top exporter has sent shockwaves through markets. "Riyadh’s threat to discount its crude and raise production prompted the price of Brent crude, the international oil marker, to fall to as low as $31.02 a barrel. West Texas Intermediate, the US benchmark, fell to $27.71 a barrel." Writing in the Financial Times, Anjli Raval and David Sheppard report.