The irony probably wasn't lost on Silvio Berlusconi on the evening of 8 November when, with bitter reluctance, the tycoon-premier told President Giorgio Napolitano that he would quit in just weeks or days to halt the disastrous downward slide of Italy's stock market. Mr Berlusconi entered politics 17 years ago to save his business interests – at that time from left-wing politicians who wanted to dismantle them. Three weeks ago he was quitting office for the very same reason; only this time it was the markets that threatened his media empire.

With the speculators singling out Italy, it was Mediaset that felt the full force of their attack. The company had already lost 20 per cent of its value in five days, but on 8 November the fall accelerated. A day earlier Mr Berlusconi had met with Fedele Confalonieri, chairman of Mediaset and his oldest and closest friend who is widely believed to have told his boss that the game for him as Prime Minister was up – and that by failing to step down immediately, he risked seeing his business empire fall with him.

"He clearly told Mr Berlusconi: 'Quit now or you'll bring the company down'," the leading Italian media analyst Alessandro Baj Badino of Deutsche Bank, told The Independent.

Mediaset's share price fell further on the 9 November, but few doubt it would have been worse had he stayed.

This version of events is supported by the remarks of Mr Berlusconi's son, Pier Silvio, in an interview in Corriere della Sera newspaper on 19 November. Berlusconi junior, Mediaset's vice-president, spoke candidly about what he saw as the "climate of hostility" surrounding Mediaset because of its links to the Prime Minister, of which his father was "well aware". And on Friday last week Mr Berlusconi's coalition ally Umberto Bossi told journalists how he had heard Mediaset bosses telling the former premier to quit.

But Mr Berlusconi's decision to step down brings huge legal risks. Despite the concern about his crumbling parliamentary and public support, Mr Berlusconi's instinct to cling on to high office was underpinned by the knowledge that quitting would leave him more vulnerable to Milan's magistrates who are trying to convict him in three criminal cases.

Mr Berlusconi's ad hoc laws providing him with immunity from prosecution have all been thrown out by the constitutional court. But, as head of government, he was able to avoid court appearances that clashed with prime ministerial engagements, thereby slowing up trials – and making it more likely that the statutes of limitations, already modified to his own advantage, would kill off at least one of the processes. Similar legal manoeuvres in the past have seen him beat criminal convictions.

The legal pressure is not letting up. Depending on which source you believe, Mr Berlusconi faces between 20 and 40 court appearances between now and May, in three ongoing trials.

One of those could come today, when he resumes his defence against the charge that he bribed the British lawyer David Mills with $600,000 (£398,000). He also faces the charge of tax fraud relating to his Mediaset empire and – in the most recent and salacious trial – of sex with a minor and abuse of office. The Mills bribery trial will certainly die under the statute of limitations early next year before the automatic appeals process can even begin, although magistrates will be eager to bag a symbolic initial guilty verdict. Neither are prosecutors likely to get a definitive conviction against him in the Mediaset tax fraud trial, which involves complex and hoary accounting trails across several continents.

Their best bet for a conviction rests with the more recent and more straightforward "Rubygate" sex and corruption trial. In another ironic twist, one of the laws Mr Berlusconi himself passed, which lowers the burden of proof required in such sex cases, may yet come back to haunt him.

And if all of this weren't enough, the accusations of Mafia association have never been far away. A reminder came last week, when a prosecutor told a Palermo court that one of the mogul's oldest and closest associates, Senator Marcello Dell'Utri, a founding member of Mr Berlusconi's original Forza Italia party, was the intermediary between the ex-premier and Cosa Nostra bosses.

Even with a definitive conviction, sentencing guidelines mean that Mr Berlusconi, as a septuagenarian, will not go to prison. But he clearly hasn't given up efforts to maintain his political power base in the possibility it might once again strengthen his hand legally.

Even before stepping down, the media mogul had offered Mr Monti the support of all his PDL MPs in exchange for guarantees on justice legislation that might work to his advantage, one Italian news agency reported. Mr Monti was said quickly to have refused the offer.

Many pundits say it is not beyond the bounds of possibility that Mr Berlusconi will make a fourth bid for high office. The political scientist Franco Panvoncello, of Rome's John Cabot University noted that "he's still the only prominent figure that people know and might want to vote for". Despite promising not to stand again, and naming the man he would like to succeed him – PDL secretary Angelino Alfano – Mr Berlusconi has been as busy as ever in the last two weeks marshalling parliamentary supporters, while the new Prime Minister Mario Monti does the dirty work of introducing new taxes and dismantling vested interests.

Mr Alfano, a politician with a face for radio in a parliamentary party full of pretty yet scantily qualified young women, has already had his credibility dented by attempting and failing three times to introduce unconstitutional immunity laws to keep Mr Berlusconi out of the courts. "If Mr Alfano stood, more experienced politicians like Roberto Formigoni [the PDL governor of Lombardy] would eat him for dinner," says Professor James Walston of the American University of Rome.

And Paolo Flores d'Arcais, the editor of the Italian magazine MicroMega, notes that, while Mr Berlusconi is no longer premier, "Berlusconismo is far from finished". He says that most of Mr Berlusconi's self-serving legislation remains in place as does his "monopolistic domination" of Italian television. "Only when this deluge of illegality has been properly dismantled can we claim that the post-Berlusconi era has really begun," he said.

Silvio's trials: from bribery to Bunga Bunga

BRIBERY CASE: BEGAN MARCH 2007, NEXT HEARING TODAY

Mr Berlusconi is accused of paying British lawyer David Mills, the estranged husband of former Olympics minister Tessa Jowell, $600,000 to lie under oath in two corruption trials in the late 1990s involving Mr Berlusconi. He was sentenced in February 2009 to four and a half years in jail for accepting a bribe from Mr Berlusconi. Criminal charges against Mr Mills were thrown out only in February of last year when time for an appeal expired under the statute of limitations. The charges against Mr Berlusconi await a similar fate, with the process due to expire by March 2013.

TAX FRAUD CASE: BEGAN NOVEMBER 2006, NEXT HEARING WEDNESDAY

In this complex case, Mr Berlusconi faces charges of tax fraud in relation to the purchase of US film rights for his television company, Mediaset. Milan magistrates claim that since the 1980s, Mr Berlusconi's holding company Fininvest, and subsequently his broadcast group Mediaset, registered inflated costs for the purchase of US film rights, in order to divert millions of euros to slush funds in Switzerland and Hong Kong. This case is also due to expire next year under the statute of limitations.

Mr Berlusconi's son Pier Silvio has been indicted in a similar case, which involved tax fraud relating to a later period.

RUBYGATE: BEGAN APRIL 2011, NEXT HEARING 2 DECEMBER

Prosecutors say Mr Berlusconi paid to have sex with a Moroccan dancer, Karima el-Mahroug, known as Ruby, at one of his adult parties at his mansion near Milan in May last year when she was just 17 years old. In Italy, paying for sex with someone under 18 is punishable with three years in jail. They also claim that Mr Berlusconi telephoned Milan police and claimed that Ms El-Mahroug was the niece or granddaughter of the then-Egyptian president, Hosni Mubarak, when she was held on suspected theft. The prosecutors allege that the premier intervened – and abused his powers – to prevent her spilling the beans on his X-rated soirées. An initial verdict is expected late next year or early 2013.

A court last week said that the witnesses could include the US actor George Clooney and the footballer Cristiano Ronaldo.

http://www.independent.co.uk/news/world/europe/can-the-law-catch-up-with-berlusconi-6268898.html