PERHAPS the most extraordinary fact about the audacious drone attack on the heart of Saudi Arabia’s oil industry was that no one saw it coming. Four months ago, the Yemeni rebels, who have claimed responsibility for crippling half the output of the world’s top oil exporter, gave a warning. It came in the form of drone attacks on Saudi oil-pumping stations and a pipeline. But no one thought that they had the capability — or the sheer audacity — to hit the Arab kingdom’s biggest oil-processing centre more than 400 miles from the Yemeni border.

Yet, should we be surprised? For the past four years, Saudi Arabian jets have been bombarding the Houthi rebels in an attempt to prevent their overthrowing the Yemeni government. The civil war in Yemen is a complex conflict, but it has been simplified down by the fact that the Houthis are Shia Muslims — as is the population of Iran, whose government backs the insurgents in Yemen in their struggle against the corrupt and authoritarian Hadi regime.

This has alarmed the Sunni Arab states in the region, led by the Saudis, who began a vicious air bombardment that was aimed at bolstering the Hadi government. In the firing line, the people of Yemen have been subjected to the worst man-made humanitarian disaster anywhere today.

Tens of thousands have been killed and injured by the air strikes, which receive logistical and intelligence support from Britain, France, and the United States. As many as 24 million people are in need of food aid. Two million children are acutely malnourished. A quarter of a million people are facing what the United Nations calls “catastrophic levels of hunger”.

Yemen has become the battleground in a proxy war between the great Shia and Sunni powers of the region. In those circumstances, it is odd that it did not occur to the international community that Houthi forces might hit back by extending the conflict beyond their homeland and into that of the power that is inflicting such devastation upon the Yemeni people.

Common sense should have prevailed in this conflict long ago. It has not — and continues not to do so. The response of President Trump to the attack was to blame Iran and to declare that the US was “locked and loaded” and ready to respond as soon as the Saudis confirmed that the Iranians were to blame. But reports suggest that the drones were launched not from Iran, nor from Yemen, but from Iraq, although it is impossible to say who may have been responsible there.

The time has come for Britain to take some responsibility in this situation. The usual argument against doing so is that our defence industry relies on arms exports to the Saudis. But the reality, according to a new report by the Center for International Policy think tank in Washington, is that Riyadh has become so dependent on American, British, and French arms that it would find it difficult to switch overnight to suppliers such as Russia or China, who sell totally incompatible equipment. That gives the West a degree of leverage over the Saudis. It is time to use it to end this cruel and pointless war in Yemen.