Canalis was there as 82-year-old billionaire Richard Lugner’s guest and she chose to wear a daring red Vivienne Westwood dress, which left her with an exposed breast (NSFW) after too many twirls on the dance floor.

Canalis, an Italian model, famously dated Hollywood actor George Clooney for two years before they split in 2011.

Lugner pays vast sums to have a glamorous celebrity on his arm at the annual Opera ball. The pair were also joined by the construction tycoon’s new wife, former Playboy model Cathy Schmitz, who is 25.

Canalis laughed off what's being referred to by some Austrian papers as "nipplegate" and seemed to be having a good time, telling reporters that it was “really beautiful and the singers are wonderful. It’s something you have to experience.” She said she had no trouble conversing with the heavily indebted Lugner, who is not known for speaking very good English.

Over 5,000 guests turned up to the sold-out ball in Vienna’s State Opera. Austrian actor Helmut Berger appeared in a wheelchair, with his toenails painted red and Naomi Campbell came with her friend Kathrin Glock (the wife of firearms company founder Gaston Glock).

Tickets to the ball start at €270 and a box in the Opera House costs more than €20,000.

It is one of the most exclusive events in the Viennese social calendar and is always kicked off with 186 debutantes and their partners dancing the opening waltz.

Vienna hosts more than 450 balls every year, including a magician’s ball, a confectioner’s ball and a coffee makers ball.