It is virtually inevitable that Putin will next year become Russia's president again. What will that mean for Russia, the world, and indeed the man who just can't seem to give up power?

The year is 2024. The world's economic prospects have perked up a bit since the collapse of the euro. The Germans are happily spending deutchmarks again, the Greeks are back with the drachma. Almost all of the leaders in power a decade earlier have been swept away – Angela Merkel, David Cameron, and Nick Clegg (remember him?). Even Silvio Berlusconi has reluctantly accepted retirement. Italy's former premier now spends his days in his Sardinian villa with a group of showgirls.

Only one leader has defied the iron law that all politicians eventually leave office. His name? Vladimir Putin. Now 71, Putin has served two more terms as Russia's president – bringing the tally of his stints in the Kremlin up to a remarkable four – the final two lasting a total of 12 years. He is fitter and more vigorous than ever: Russian first state TV channel has recently shown him wrestling heroically with a python after it "escaped" from a Moscow zoo.

In theory, this is the moment when Putin should finally step down after a quarter of century at the apex of Russian power. He has already outlasted Leonid Brezhnev (18 years) and is closing in fast on comrade Stalin (a whopping 31).

Ridiculous predictions? Well, no. On Saturday Putin announced that he was standing for a third term as president in "elections" to be held next March. The man who has been keeping the Kremlin seat warm for him, Dmitry Medvedev, is to become Russia's prime minister. It's time to switch! At the Putin-led United Russia party conference, Medvedev endorsed Putin's triumphant return; the two men hugged, Medvedev's grin, admittedly, somewhat strained.

The news was, somehow, a bombshell and no surprise whatsoever. Over the past four years, poor Medvedev has had to live with the slur that – despite occupying the role of president – he was subservient to Putin, Russia's prime minister but pre-eminent leader. The jibes have been hurtful because they are true. It now appears that back in 2007, before he took the job, Medvedev had agreed to stand aside after one stint – in a sort of un-Granita pact.

Leaked last year, secret US cables offer an amusing portrait of the Putin/Medvedev relationship – an anomalous arrangement for Russia known as the "tandem". Traditionally, of course, Russia has always had one-man (or one-woman) authoritarian rule. Think Peter I, Catherine II, and Alexander III; Lenin, Stalin etc. The tandem was an unprecedented break with this historical tradition of conservative autocracy.

Reading through these dispatches last year, I was struck by the slightly desperate but nevertheless creative way US analysts tried to make sense of impenetrable Kremlin politics. One cable by Eric Rubin, US deputy ambassador, suggested that Medvedev played Robin to Putin's Batman. It was a good analogy; it whizzed round the world, prompting Putin to complain of US "arrogance".

Other comparisons were equally unflattering. US diplomats cabled back to Washington the widely held view that Medvedev was the "junior partner", or Putin's "capable assistant". In the words of one scathing opposition politician he was "the Lilliputian to Putin's commander-in-chief." At a reputed 5ft 2in Medvedev is one of the shortest world leaders ever. It is "Putin who is pulling the strings," I read.

Another delightful comparison likened Putin to Cardinal Richelieu, with Medvedev cast in the role of Louis XIII.

At the beginning of Medvedev's presidential term, diplomats, political observers and journalists raked over Medvedev's CV in search of clues. He was famously a fan of the superannuated British rockers Deep Purple. Did this mean that Medvedev would usher in a new, more friendly, era in London-Moscow relations? Or did it merely confirm that Medvedev was a bit of geek?

Despite all the evidence to the contrary, there was a vague optimism that Medvedev might just preside over a partial liberalisation of Russian society, after the rollback under Putin between 2000-2008 of democracy and basic rights. For starters, Mededvev had no background in Russia's sinister security services. He talked of reform and modernisation. Perhaps, then, Russia was finally moving away from its lugubrious KGB track.

By 2010, however, more or less everyone had concluded that Medvedev and his "liberal" agenda were phoney. Most correspondents stopped reporting Medvedev's speeches. They had become boring and lacking in credibility.

In some of the last dispatches released by WikiLeaks, US diplomats correctly predicted that Russia's "bicephalous ruling format" was fizzling out. "His [Putin's] return to the Kremlin is not inevitable. But should things remain stable Putin remains in a position to choose himself, Medvedev or another person to become Russia's next president," diplomat Susan Elliott wrote.

It's no shock, then, that, having carefully weighed up the options, Putin decided to choose himself to be Russia's next president. His election is a foregone conclusion: in previous polls, opposition candidates and anti-Kremlin parties fail to make it on to the ballot paper. With Russian state TV having morphed into a daily Putin/Medvedev blog, Putin can expect blanket positive coverage ahead of his coronation. No doubt there will be more macho photo-opportunities. Putin recently turned up to a convention of bikers, dressed in black and riding a Harley – merely one of a succession of stunts that has seen him ski down a volcano, pose with a polar bear and dive to the bottom of Russia's Lake Baikal in a submersible. He even appears now to have had a bit of face-work done.

So what now? The winds of change may be blowing across the Arab world, rolling from Egypt to Tripoli's Green Square. But Russians are looking at an endless Putin epoch, and a long period of political stagnation.

It's a bleak prospect. Liberals in Moscow and St Petersburg were yesterday posting a photo of Putin mocked up to look like Leonid Brezhnev – complete with military uniform, patriotic Soviet medals and a hammer and sickle. Putin even got Brezhnevian eyebrows.

Actually, the comparisons with the Brezhnev era are spot-on. Brezhnev presided over another era of political and economic stagnation, the 1970s, sustained by a commodities boom and high oil prices. He also had a war – he sent the Red Army to invade Afghanistan. In 2008 Putin did the same thing. He sent Russian tanks into Georgia, promising to hang Georgia's pro-western leader Mikheil Saakashvili "by the balls". It was a brutal lesson in neighbourhood geopolitics.

Brezhnev also presided over an Olympics – Moscow, 1980. Putin has the 2014 Winter Olympics in Sochi to look forward to, as well as the 2018 World Cup. (The scenario is already tantalising: an ignominious first-round exit by England after an off-form Wayne Rooney falls mysteriously ill with food poisoning. Foul play is discounted since England play so badly anyway. The Russian team sweeps to victory on the back of patriotic fervour and a curious offside decision.)

International reaction to the weekend's news has hardly been ecstatic. Putin's world view is reflexively anti-western. He doesn't believe western countries are genuine democracies. He is by temperament suspicious and prone to a belief in conspiracies. The Obama administration put out a bland statement confirming that its "reset" with the Kremlin will go on. Privately, however, the White House will certainly not be delighted at the prospect of dealing with prickly President Putin again. The US administration's attempts to make Medvedev the "primary interlocutor" in negotiations – and to boost the "more progressive" forces he supposedly represented – were, alas, a waste of time.

To be fair, US diplomats always recognised that Putin was in charge, and that he was responsible for the recent modest improvement in relations following a period of mutual acrimony during the last years of the Bush White House. One 2009 dispatch by the US ambassador John Beyrle puts it like this: "We are not advocating circumventing Putin; to the contrary we cannot imagine improved US-Russian relations with his concurrence." Beyrle also talks about "managing Putin and his ego".

Relations with Britain are unlikely to get much better either. Andrei Lugovoi – the man who allegedly slipped radioactive polonium into former KGB agent Alexander Litvinenko's tea – enjoys the personal protection of Putin. When the CPS requested his extradition in 2007, Putin responded by lambasting Britain's colonial "no brains" mentality. David Cameron did manage to meet Putin in Moscow this month, the first contact for four years. But it's safe to assume that President Putin won't be visiting London anytime soon.

The main sticking point is the row with Russia's FSB spy agency – the same agency that Putin headed before he became president in 2000.

Britain is convinced that there is an FSB dimension to Litvinenko's murder. It severed contact with it in 2007. The Kremlin sees this as humiliating. It wants cooperation with the FSB to resume. And it has made this a precondition of better relations. The ball is in Cameron's court – or in someone else's court when his Conservative-led coalition shuffles off into history.

Some commentators have persuasively suggested that Putin is tired of being Russia's leader. He would like nothing better, they argue, than to relax in his new palace in Sochi, on Russia's balmy Black Sea coast. The logic, however, of Putin's corrupt vertical state, is that he is forced to carry on. Putin is the only person capable of arbitrating between the Kremlin's rival factions, who are locked in a permanent and exhausting battle for money and influence. Without him, the system would fall apart.

Most crucially, Putin faces the prospect of law enforcement investigations into his alleged secret assets, should he ever decide to step off the throne. According to US diplomats, his main motivation for carrying on is to guarantee the safety of his own assets and those of his inner circle. No one quite knows how much Putin and his friends are worth. (Several of them feature prominently on the Forbes annual list.) But the sums involved allegedly total many billions of dollars.

All this, of course, assumes that there is no revolution. With no prospect of removing Putin from power peacefully, and the Kremlin's succession politics as byzantine as ever, could it be a matter of time before Russians take things into their own hands? True, Putin is still Russia's most popular politician. But he is less popular than he was. And while his return to the Kremlin is guaranteed, his nervousness that he may one day be overthrown can only grow.