In 2017 liberal democracies came under pressure from inside and out. The new year opened with a reminder that autocracies can be brittle, too.

The street protests that have swept across much of Iran in recent days have gathered momentum in a way that is virtually unprecedented in the nearly four decades since the revolution that deposed the shah. The ensuing crackdown will probably work. But Iran’s leadership should heed the warning signs. Iranians are tiring of a regime that squanders resources on foreign adventures, instead of devoting them to development at home.

Popular frustration has been fuelled at least partly by unmet expectations. The re-elected centrist president Hassan Rouhani’s tentative rapprochement with the west held out the promise of an opening. Underpinned by the 2015 agreement to freeze some nuclear activities in return for the lifting of sanctions, the deal raised hopes among Iranians of re-engagement with the world and re-entry into global markets. But it has both whetted Iranian appetite for more change and failed to deliver in a practical sense.