Suddenly, the fragile foundation on which Russia’s ruling oligarchy rests has been exposed. Who would have imagined that Yevgeny Prigozhin’s mercenary Wagner Group, so central to Russia’s barbaric invasion of Ukraine, would turn on Vladimir Putin and launch an armed insurrection inside Russian territory?

When Prigozhin told the world yesterday that the Russian military had deliberately shelled a Wagner camp, and that he and his army were crossing the border from Ukraine into Russia, with the aim of overthrowing Russia’s military leadership, he effectively called into question the legitimacy of Putin’s rule.

The ease with which his troops took control of military buildings and the airport in the city of Rostov indicates that the Russian army is neither an effective nor a reliable force. Crossing the Rubicon has never seemed easier.