Riyadh has just put in a huge order for 15,000 US-made Raytheon BGM-71 anti-tank missiles costing more than $1 bn. They include the most advanced version of the tube-launched, optically tracked, wire-guided (TOW) missiles. Since no one expects a tank invasion of the oil kingdom any time soon, Middle East strategists believe they are destined for Saudi-backed Syrian rebel militias to get round the Obama administrations refusal to let them have heavy weapons. When last checked, the Saudis had more than 4,000 anti-tank missiles in stock, purchased for their own use in 2009.