WHEN King Salman acceded to the Saudi throne in 2015, it was plain that his son, Muhammad, wielded the real power. He may formally have been second in the line of succession, but Muhammad bin Salman (known as MBS) ran most of the things that mattered: the plan to transform the Saudi state and wean the economy away from oil; the war in Yemen and the wider contest against Shia Iran; and much else besides. When he gave his first on-the-record interview, to The Economistin January 2016, MBS spoke about Saudi Arabia in the first person—talking of “my borders”.

On the face of it, the elevation of MBS to crown prince, replacing his older cousin, Muhammad bin Nayef, means only that his job title has caught up with reality (see article). Yet it rewrites the kingdom’s strange rules of succession. Whereas power once passed along the line of ageing sons of King Abdel Aziz Al Saud, the state’s founder, it now goes down the blood line of King Salman. No one would be surprised if Salman, who is 81, were to abdicate in favour of his 31-year-old heir.

Intelligent, ambitious and willing to entertain new ideas, MBS shows much promise, but a worrying tendency to act rashly. Abroad, he pushed his country to intervene in Yemen’s civil war. This is now in its third year and has reached a grim stalemate; Yemenis, already the poorest Arab nation, have become even more wretched through bloodshed, hunger and disease. MBS is also thought to be behind the recent diplomatic assault on Qatar. Saudi Arabia and several Arab countries have cut land, sea and air links with the emirate, on vague accusations that it supports terrorism (a charge often levelled at the Saudis, too).

At home, MBS presides over a country still too dependent on hydrocarbons. His gamble of allowing oil prices to fall to drive out high-cost producers failed. More recently, an attempt to support prices by co-ordinated production cuts has not worked either. Now the Saudis face the worst of all worlds: low oil prices and a falling market share for their crude.

This will make it harder for the prince to remake the Saudi state and economy. His plan, known as Saudi Vision 2030, is a radical programme of privatisation (cuts in subsidies and investments in non-oil industries). The first really big step is supposed to be the sale of 5% of the shares in Saudi Aramco, the world’s largest oil company (see article). This would be the world’s biggest listing—even if Aramco is worth less than the $2trn that MBS places on it. The company is streamlining itself to look more like a public company. Tax rates on Aramco’s profits have been slashed from 85% to 50%, closer to international norms. But the prince’s tendency to micromanage and play politics with the listing worries investors.

A young prince in a hurry

Saudis largely agree that their system of bountiful benefits and do-nothing public-sector jobs needs to change. But few welcome austerity. Faced with a backlash, the prince has revoked cuts in allowances and bonuses for civil servants; soldiers fighting in Yemen were given a two-month pay bonus. Some princes now mockingly call MBS al-walad (the boy). Despite these difficulties, or perhaps because of them, MBS is hurrying to consolidate his power. He may feel encouraged by the gung-ho way that President Donald Trump has aligned America with Saudi interests, as defined by MBS, supporting the isolation of Qatar against the better judgment of Rex Tillerson and James Mattis, the secretaries of state and defence.

Saudi Arabia matters immensely, both as a swing producer of oil and as the birthplace of Islam. It has avoided the bloody upheaval that has rocked the Arab world of late, but its stability is far from assured. So reform is urgent. MBS should share some power with modernising princes, while checking the excesses of religious reactionaries and the sprawling royal family. He should relax strict social controls, particularly on women, and encourage more debate and dissent. He should halt the pointless row with Qatar, and seek a political deal to end the war in Yemen. That way he can focus on his biggest task: turning his country’s rentier economy into something more dynamic. Having created a huge job for himself, MBS will be judged on whether he creates lots of jobs for young Saudis.