After more than 26 months, 50 court hearings and countless breathless column inches from journalists worldwide, it took just four minutes for the sentence that Silvio Berlusconi had feared to be delivered. At 5.19pm, before a fascist-era sculpture showing two men struck down by a towering figure, the judges swept into the courtroom and pronounced their damning verdict for Italy's longest-serving postwar prime minister. By 5.23pm, it was all over.

At the culmination of a trial that helped strike the final nail in the coffin of the playboy politician's international reputation, the judges found Berlusconi guilty both of paying for sex with the underage prostitute nicknamed Ruby Heartstealer and abusing his office to cover it up. They even went beyond the prosecutors' sentencing requests, ordering him to serve seven – rather than six – years in prison and face a lifetime ban on holding public office.

Perhaps fittingly for a case that cast a spotlight on the murky nexus of sex and power that prosecutors argued was at the heart of his premiership – in which young women were procured, they said, "for the personal sexual satisfaction" of the billionaire septuagenarian – all three judges were female.

Berlusconi, who had been predicting the verdict for weeks as the logical result of his lifelong "persecution" by leftwing prosecutors, has always denied the charges and now has the right to lodge not one but two appeals. The sentence will be enforced only if these fail and it is made definitive, a process that could take years. Regardless of whether it is eventually upheld, Berlusconi is highly unlikely ever to go to jail.

There were some notable absentees in court on Monday: Ilda Boccassini, the formidable prosecutor who had led the case against the 76-year-old, and Karima el-Mahroug, the former nightclub dancer from Morocco whom Berlusconi was convicted of paying for sex in 2010 when she was 17, below the legal age of prostitution in Italy. Both he and she denied having "intimate relations" and claimed the thousands of euros he gave her were simply the support of a generous friend.

The more serious charge, however, was that in May of that year he exerted prime-ministerial pressure on police in Milan to release Mahroug from custody for fear she would reveal details of their liaisons. He admitted having made a call to police, but said he did so in the belief that her detention might cause a "diplomatic incident" because he believed her to be a relative of Hosni Mubarak, then the president of Egypt.

Berlusconi himself also chose to stay away from the court. The leader of the centre-right Freedom People (PdL) party was reported to have waited for the verdict at the Villa San Martino in Arcore, scene of the by-now infamous "bunga bunga" parties where, prosecutors argued, he held raucous evenings of striptease and sex with young women he remunerated handsomely.

Afterwards, he expressed outrage at the verdict, which he said was politically motivated. "An incredible sentence has been issued of a violence never seen or heard of before, to try to eliminate me from the political life of this country," Berlusconi said in a statement.

"Yet again I intend to resist against this persecution because I am absolutely innocent and I don't want in any way to abandon my battle to make Italy a country that is truly free and just."

One of his staunchest allies, the PdL MP Daniela Santanché, had listened to the sentencing in immaculate disbelief. "This is a political sentence that has nothing to do with justice," she told swarms of reporters trailing after her down the stairs of Milan's vast palazzo di giustizia. "These women have used other women for political motives. The defence lawyer Niccolò Ghedini said the sentence was "beyond reality".

For many Italians, however, the verdict was entirely proportionate. Ever since the first media reports emerged in 2010 and the then prime minister was placed under formal investigation in January 2011, the drip-feed of sordid details from Arcore via the courtroom has tested traditional tolerance towards politicians' private lives.

The prosecutors argued that, rather than the innocent, elegant dinner parties of Berlusconi's claims, the soirées were in fact a chance for the then prime minister to procure the sexual services of a variety of women. Two witnesses told investigators of an eyebrow-raising game involving a statue of the fertility god Priapus; in a separate but related trial, Mahroug testified that women had dressed up as nuns and nurses before stripping. On one notable occasion, she claimed, one had even paraded alternately as Barack Obama and the flame-haired Boccassini.

One person who will be less than delighted by the verdict is Enrico Letta, Italy's current prime minister, who has the unenviable task of holding together a fraught grand coalition of his centre-left and Berlusconi's centre-right. Although he occupies no ministry, Berlusconi still plays an influential role in national politics, and he has the power – as Letta is acutely aware – to bring it down by withdrawing his support and triggering new elections.

Some observers say that the verdict – which showed that even in his latest incarnation of benevolent, self-sacrificing statesman, he is not protected from the long arm of the law – may have brought that a step closer. Tensions were made clear in a curt statement by Angelino Alfano, PdL secretary and deputy prime minister. The sentence was, he said, "contrary to common judicial sense, good sense, and worse than the worst expected".

Others, however, predict Berlusconi will make no immediate move, preferring to keep up pressure on Italy's supreme court before another, less salacious but potentially far more damaging verdict, expected by the end of the year: the definitive ruling on tax fraud charges for which he is approaching the last roll of the dice.

If the court of cassation upholds his conviction, he will face not only a four-year jail sentence but also – more pertinently for a man whose political ambitions have never died – a five-year ban on public office. For many people, though, the verdict was already quite something. "A conviction to save the dignity of Italy," read the placard of a woman standing outside the courthouse with an all-female group singing the Italian Resistance song "Bella ciao" ("Bye-bye, beautiful"). Another declared: "Berlusconi is ineligible, unsupportable, unpresentable."