No one doubted that Crown Prince Mohammed bin Salman was a man in a hurry. But the Saudi royal’s decision to arrest 11 princes, four ministers and dozens of former ministers shows he is a risk-taker on a scale the Middle East has rarely seen.

The fact that the billionaire Prince Alwaleed bin Talal, who owns the investment firm Kingdom Holding, was among the wave of late-night arrests (and is thought to be held in the luxurious confines of Riyadh’s Ritz Carlton hotel) suggests MBS, as Salman is known colloquially, is willing to take on the kingdom’s most powerful figures to implement his reforms and consolidate power.

In theory, MBS could be in power for a half a century. The question is whether he is showing the maturity and steadiness to use such a lengthy reign to create a viable, modern Saudi Arabia.

The crown prince will say the arrests show his determination to root out corruption, a precondition of a more open economy. But few think the arrests, and related ministerial sackings, are the independent decision of a new corruption body, established just hours before to replace an existing one, rather than part of a wider reshuffle to centralise all security authority under MBS.

The speed and unpredictability with which the crown prince acts – the purge was undertaken in great secrecy in the early hours of Sunday morning – is part of a pattern of behaviour unlikely to reassure international investors and interlocutors.

After all, MBS effectively seized power in a palace coup in June, ousting his elder cousin Mohammad bin Nayef as heir to the throne and interior minister. Since then, the pace of reform has been breathtaking, and contradictory.

Women are to be given the right to drive next year, cinemas are to be opened, tourists welcomed and the role of clerics driven back as part of a cultural and social revolution designed to make the secretive kingdom closer to the model of the United Arab Emirates (UAE) and tprepare the economy for life after oil.

The prince is launching a huge sale of state assets, and the UK and US are falling over each other to handle the $2tn (£1.52tn) float of Saudi Aramco, which could raise as much as $100bn for Saudi Arabia.

This cash is to be used to build a new capitalist megacity, the extraordinary plans for which were unveiled last week. Many of the Saudi businessmen present at the unveiling are now locked up in the Ritz Carlton, with their phones cut off not just from room service, but their lawyers.

MBS has been equally bold in his foreign policy, determined to curb Shia Iran and marginalise Saudi’s Sunni rival Qatar. Saudi has launched an unending and brutal war in Yemen designed to quell the Iranian-backed Houthis. A missile was launched towards Riyadh this weekend in a sign of how the Saudis are struggling to secure a military victory.

In June, MBS imposed a politically costly economic boycott on Qatar that has lost it allies in Europe and Washington. This weekend, the Sunni leader in Lebanon, Saad Hariri, under pressure from MBS, quit as prime minister in order to isolate Hezbollah and deepen the conflict with Iran.

In addition, the Saudis are trying to force the weakened Syrian opposition to rein back its demands to end the civil war, in what looks like an uneasy alliance with Russia.

It is a programme of social, economic and political reform, largely backed by the UAE, that amounts to a revolution in one of the most conservative countries in the world. The test is whether MBS has taken on too much at once. His latest purge is a sign that he knows opposition is gathering, and believes the educated population, liberated by social media, want reforms to go faster, and those holding back change must be ruthlesslyset aside.

The list of the latest detainees is breathtaking – the equivalent of Theresa May sacking half her cabinet. As well as Prince al-Waleed, the roll call includes the former finance minister Ibrahim al-Assaf, a board member of national oil giant Saudi Aramco; the economy minister Adel Fakieh, who once played a major role in drafting reforms; the former Riyadh governor Prince Turki bin Abdullah; and Khalid al-Tuwaijiri, who headed the royal court under the late King Abdullah.

Bakr bin Laden, chairman of the Saudi Binladin construction group, and Alwaleed al-Ibrahim, owner of the MBC television network, were also detained.

Stock markets have recovered from the shock of the arrests, and MBS is the last man standing. But the reverberations of Saturday’s night of the long knives may just be starting.