The scene inside the opulent ballroom of Vienna's Hofburg Palace could have been lifted straight from The Sound of Music: young women in swishing dirndl dresses linked hands under chandeliers with students in traditional loden suits as they gently waltzed in formation to the rhythmic orchestral sound of Johann Strauss.
But in the streets outside the building last Friday evening, the spectacle was radically different. Phalanxes of white-helmeted Austrian riot police stood equipped with shields and truncheons.
"Nazis Piss Off, Nobody Misses You!" read one of the banners held aloft by demonstrators. Ugly scuffles ensued. One man was reported to have been arrested after being caught carrying a kilo of explosives.
The event they were so vociferously objecting to was a traditional Vienna student ball known as the "Korporierten-Fest". Started in 1952 as part of Vienna's traditional ball season, the student ball has gained an unsavoury reputation for being a white-tie extravaganza for the elite of Europeans' political far right.
The scenes are bound to be an embarrassment to the Viennese ball tradition in general, considered a cultural treasure in Austria. Each season sees more than 250 balls held across the city, where streams of debutants are paraded in white dresses. The season runs from 31 December until early March, and the proceeds often go to charity. The most high profile is the Opera Ball, which has in the past been attended by everyone from the Duchess of York to Paris Hilton.
It is not the first embarrassment caused by Korporierten-Fest's shady far-right links. The United Nations cultural arm, UNESCO dropped the entire Viennese ball concept from its list of Austrian cultural traditions last month after protests from anti-fascist campaigners. UNESCO said the student ball – which is the only one in the programme with such political connections – had failed to live up to its principles which gave a "special priority to tolerance and respect for other cultures".
Its far right reputation was dutifully upheld last Friday. Hosted by Heinz-Christian Strache, leader of the far-right Freedom Party, guests included Marine Le Pen, the leader of France's National Front, and representatives from the Belgian far right party Vlaams Belang.
Asked by the French daily Liberation, why his daughter chose to attend an event which had been discredited for being so demonstrably far right, her father, the veteran National Front founder, Jean Marie Le Pen, replied with his characteristic brand of racist humour: "It reminds me of 19th century Vienna – it's Strauss without the Kahn."
The Viennese ball might have escaped with UNESCO's rap on the knuckles, had it not been for an initially unreported anti-Semitic tirade delivered from Strache's ballroom box to some 3,000 of his right wing guests last Friday, describing Austria's far-right as the "New Jews".
By yesterday it had become the focus of a blistering political row about everyday anti-Semitism and the disturbing, yet seemingly inexorable, rise of popular right-wing Austrian nationalism.
Referring to the protesters outside, Mr Strache told his audience they should not be prepared to have their "wonderful cultural party" ruined by protesters whom he described as "anti-democratic perpetrators of violence". He then claimed the violence outside was like "Kristallnacht" – the 1938 Nazi pogrom that foreshadowed the Holocaust – and declared to his ball guests: "We are the new Jews!" Reports in the Austrian press subsequently revealed that Strache's Freedom Party aide, Klaus Nittmann, had referred to the yellow star the Nazi regime forced Jews to wear and told ball guests: "Organisations behind the ball end up getting a Jewish Star pinned on them."
And in what was seen by many as adding insult to injury, last Friday's Vienna student ball just happened to fall on Holocaust remembrance day – the anniversary of the Soviet army's liberation of the Auschwitz death camp. Eva Glawischnig, head of Austria's Green Party, suggested that those who attended were effectively "dancing on the graves of Auschwitz". The organisers chose to ignore the charge.
Austria's Jewish community has since been sufficiently outraged and insulted to demand that state prosecutors investigate Strache. Austria's ruling centrist People's Party described his words as a "slap in the face for all victims of the Nazis' criminal regime". Strache's Freedom Party dismissed the criticism as "artificial and ridiculous outrage", while Strache himself said he did not intend to "play down the agony forced upon the Jews".
Yet his outburst has raised more disturbing questions about his party, an organisation which is now Austria's second political force. It made huge gains in recent Vienna city elections with a virulently Islamophobic campaign.
One gimmick included a computer game in which contestants could shoot at mosques and minarets. If the party's 42-year-old leader – a trained dental technician – gets his way in next year's elections, his party could emerge as Austria's strongest. Strache is a member of one of the Austrian student clubs – "Burschenschaften" – in whose honour the country's right-wing Vienna ball is held annually.
The clubs do not only enjoy a reputation for heavy drinking. Several still practise an antiquated duelling style conducted without full face masks. The aim is to enable contestants to prove their manhood by obtaining genuine scars on their cheeks. Some 4,000 of Austria's Burschenschaft members are thought to support the far right.
The Freedom Party's increasing popularity recently led Strache to reject an invitation from a far-right student club, fearing he might be too closely identified with extremist views. In a bid to dispel concerns about his attitude to the Nazi persecution of the Jews, he also visited Israel's Jad Vashem Holocaust memorial. But instead of donning a traditional Jewish Kippa to pay respects, he chose his student cap. One Austrian Jewish leader said the spectre made him "want to throw up".