The disappearance and probable death of Jamal Khashoggi is a tragedy and a mystery. It is also a grievous blow to American policy in the Middle East.

To the extent that the Trump administration had a Middle East strategy, it centred on Saudi Arabia and the mercurial figure of Prince Mohammed bin Salman — or MbS, as he is always known. The Saudi crown prince was meant to be the man who would rally an alliance against Iran, make peace with Israel, take on the clerical establishment in his own country and help to crush Isis at home and abroad. By his own account, he would also liberalise Saudi society and transform the economy — delivering juicy deals to US companies in the process.

The centrality of Saudi Arabia to Donald Trump’s world view was underlined when the US president made his first official trip overseas to Riyadh, the Saudi capital. MbS quickly struck up a close relationship with Jared Kushner, Mr Trump’s son-in-law. Both men are in their thirties and together they plotted to remake the geopolitics of the Middle East.