Mr Putin has reversed federalism, and turned Russia into a centralised state. He cancelled regional elections, imposed a "presidential" representative over the heads of governors and redistributed tax revenues in Moscow's favour. But he did not build common institutions. The Russian state is seen not as an upholder of law but as a source of injustice and corruption.

In the words of Mikhail Iampolski, a historian, Russia now resembles a khanate in which local princes receive a licence to rule from the chief khan in the Kremlin. For the past decade, the main job of the Moscow-appointed governors has been to provide votes for Mr Putin. In exchange they received a share of oil revenues and the right to rule as they see fit. Chechnya under Ramzan Kadyrov, a former warlord installed by Mr Putin, is a grotesque illustration of this. In the most recent presidential election, Chechnya provided 99.7% of its votes for Mr Putin with a turnout of 99.6%. In return, Mr Kadyrov receives subsidies and freedom to subject his people to his own "informal" taxes and Islamic rules. Moscow pays a dictatorial and corrupt Chechnya a vast due in return for Mr Kadyrov pretending to be part of Russia and pledging loyalty to Mr Putin.

What happens if Putin goes

If Mr Putin goes and the money runs out, Chechnya could be the first to break off. This would have a dramatic effect on the rest of the north Caucasus region. Neighbouring Dagestan, a far bigger and more complex republic than Chechnya, could fragment. A conflict in the Caucasus combined with the weakness of the central government in Russia could make other regions want to detach themselves from Moscow's problems.

Tatarstan, home to 2 million Muslim ethnic Tatars and 1.5 million ethnic Russians, could declare itself the separate khanate it was in the 15th century. It has a strong identity, a diverse economy, which includes its own oil firm, and a well-educated ruling class. It would form a special relationship with Crimea, which Crimean Tartars (at last able to claim their historic land) would declare an independent state.

The Ural region could form a republic — as it tried to do in 1993 — around Yekaterinburg, Russia's fourth-largest city, or else it could form a union with Siberia. Siberia itself could revive its own identity, from a base in the cities of Krasnoyarsk and Irkutsk, and lay claim to its oil-and-gas riches, which it would sell to China. Unlike Russia, China might not have much interest in territorial expansion into the sparsely populated Far East and Siberia, but it could (and already does) colonise these regions economically. Vladivostok and Khabarovsk, two of the largest cities in the Far East, are more economically integrated with China and South Korea than they are with the European part of Russia.

Despite Russia's deep paranoia that America is trying to break it up, such a scenario is one of the West's worst nightmares. It opens the question of control over Russia's nuclear arms. Although the command centre would remain in Moscow, securing missiles spread across Russian territory could be harder than it was after the collapse of the Soviet Union. At the time, the Russians and Americans worked successfully together to move the nuclear arsenal from Ukraine and Kazakhstan to Russia. Ukraine was given a piece of paper — called the Budapest memorandum and signed by Russia, America and Britain — which guaranteed its territorial integrity in exchange for giving up its nuclear arms. Now, Russia's annexation of Crimea has made any such assurance worthless.

The spectre of disintegration is already haunting Russia. Politicians and pundits are scared to discuss it publicly. Shortly after annexing Crimea and stirring separatism in eastern Ukraine, the Kremlin introduced a law which makes "incitement of any action undermining Russia's own territorial integrity" a criminal offence. Yet the greatest threat to Russia's territorial integrity is posed by the Kremlin itself and its policies in Ukraine.

By breaking the post-Soviet borders, Mr Putin opened a Pandora's box. If Crimea "historically" belongs to Russia as he has claimed, what about Kaliningrad, the former Königsberg, an exclave which Germany lost to Russia after the second world war? Should not eastern Karelia, which Finland ceded to the Soviet Union after the winter war in 1940, be Finnish and the Kuril Islands return to Japan?

Even more perilously for Russia's future, Mr Putin brought into motion forces that thrive on war and nationalism. These are not the forces of imperial expansion — Russia lacks the dynamism, resources and vision that empire-building requires. They are forces of chaos and disorganisation. Eastern Ukraine has turned into a nest of criminals and racketeers. They cannot spread Russian civilisation, but they can spread anarchy.

In short, Russia under Mr Putin is much more fragile than it looks. Vyacheslav Volodin, his deputy chief of staff, recently equated Mr Putin with Russia: "No Putin, no Russia," he said. It is hard to think of a worse indictment.