People have been speculating for ages: how secure is Putin? How will he eventually go? Who is likely to succeed him? Surely a dictator so surrounded by sycophantic generals, spies and secret policemen could ward off any serious threat? There was no one obvious to lead a move to throw him out. Anyway, his successor might be even worse. The broad conclusion was that he could be with us for a long time.

These were always fragile arguments. No dictator foresees the coup that overthrows him. No one can follow all the intrigues from outside. All politicians eventually lose their political instincts. It took Mrs Thatcher thirteen years. Putin has been there nearly twice as long- and his position has become increasingly brittle.

When he moved centre stage as president in 2000, Putin promised the Russians prosperity, stability and the restoration of their self-respect after the chaotic poverty and humiliation of the Yeltsin years. His innate political cunning was accompanied by good fortune. High oil prices gave him the money to meet most of his popular promises. People turned a blind eye to his brutal rule and the corruption of his associates.

But he became obsessed with Ukraine. Like many of his countrymen, he resented the way it had detached itself from Russia after what they saw as centuries of intimate partnership, and he was determined to do something about it. He began by interfering directly with Ukrainian domestic politics in order to increase his own influence and reduce that of the West. Next, by means of a rather well-executed coup de main, he annexed Crimea to Russia, claiming that Ukraine had acquired it illegally as the result of an irresponsible political gesture by the Soviet leader Nikita Khrushchev six decades earlier. Then, scarcely bothering to hide what he was doing, he gave military and political support to the rebels fighting to bring Eastern Ukraine into Russia.

Finally, he launched a full-scale invasion, on the pretext that Ukrainian fascists had already begun a war with the help of the West, designed to destroy the thousand-year-old Russian state. He evidently thought that could quickly reduce  Ukraine to a vassal or take it over entirely. The Ukrainians surprised him, the West, and perhaps even themselves by the courageous ingenuity of their resistance.

Putin tried to compensate for military failure by a burst of patriotic hysteria. He then made a further massive misjudgement. No dictator in his right mind allows a subordinate to build an independent military force. But, as he ran short of Russian regular and conscript soldiers, he farmed out part of the battle to a crony from the lower depths of St Petersburg, Yevgeny Prigozhin, who contributed his own army of convicts sprung from the prisons of Russia. They were fairly effective and grotesquely brutal, but they were unable to break the Ukrainians.

Prigozhin was scornful of the incompetent way the Russian military had managed the initial stages of the war. He was deeply resentful of their attempts to gain control over him. He claimed that they were deliberately starving his men of weapons and ammunition. The war, he went on to trumpet, was nothing to do with Ukrainian Fascists: it was simply a get-rich-quick scheme devised by greedy and ambitious generals for their own benefit. This was already a serious swipe at Putin. But on 23 June Prigozhin tipped over into armed rebellion. He and his men put tanks on the streets of Rostov-on-Don, the logistics and communications hub for the Russian army in Ukraine, and took over the military headquarters there. He demanded that the military leadership come to him: otherwise he would go to Moscow to get them himself. He claimed it was not a coup, but a demand for justice.

At first Putin appears to have tried force. There are stories that Prigozhin’s men were bombarded by missiles and attacked by helicopters. But he failed to clip Prigozhin’s wings. He then accused Prigozhin on television of betraying his country and his people in their time of need, and called for his arrest. He drew a remarkably inept parallel with the events of 1917 – it’s not clear whether he was referring to the mutinies that brought down the Tsar in February оr the march on the capital by a rebellious general in August. Either way, people’s blood must have run cold as they remembered the horrors which followed that disastrous year.

Putin’s ministers and generals, his spies and his policemen, rallied round him, at least in public. So did thugs, such as Ramzan Kadyrov, who has ruled Chechnya since Putin pounded it into submission. The authorities dug up the roads to Moscow as Prigozhin and his soldiers approached. Abandoning his threat to prosecute the traitor, Putin got his crony, the Belarusian dictator Alexander Lukashenko, to negotiate a deal. Saying he wanted to avoid bloodshed, Prigozhin marched his men back down the hill. It’s not yet clear where they will end up, or who will pay for them when they get there. But as they left Rostov they were cheered on the streets.

Prigozhin bottled out and made a fool of himself. But Putin’s weakness has been shown up and his authority diminished. Much of the detail is still murky. The right-wing extremists who used to support Prigozhin are still around. We don’t know what the soldiers in the field or the wretched Russian people really think or how they will finally jump. We still have no idea how or when Putin will go, or who will succeed him. But the end of the Putin era is surely heaving into sight.

Meanwhile, Moscow has a war to fight.