Brent crude closed the year at just over $56 per barrel, down 50pc from its peak in 2014 but Mr Naimi has gone on the record to say that, even if prices fall as low as $20 per barrel, the kingdom will continue to keep its vast low-cost oil wells pumping at their current rate of about 9.5m bpd. Some Opec insiders worry that Saudi is more likely to quietly increase its production by a further 1m bpd, causing an even sharper fall in prices. At these levels, what might be seen as the kingdom’s “Berlin or Bust” strategy - with echoes of the final all-out push to defeat Germany in the First World War - risks crippling not just the kingdom’s economy but also those of its close Arab allies.