Keith Urban on why fan ‘whacked’ Nicole Kidman with a program at the opera

Nicole Kidman found out the hard way that some opera fans will not stand for a breach in etiquette during a performance.

The actor's husband, country music star Keith Urban, shared details of his run-in with an angry opera goer who struck his wife with a program when she stood up for an ovation last month at a performance of "The Merry Widow" at the Sydney Opera House.

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"We didn't know you're not supposed to stand in the opera," Urban told the "Kyle and Jackie O Show" on Australia's KIIS FM. "We're sitting down, we're with Nic's mom and we're clapping. It was a bloody great performance, it was so good, and I'm looking around, and we're cheering and cheering, everybody's cheering, and I look around and I see a few people standing, and a few more, and I went, 'Oh, bloody hell, I'm getting up.

"And I stood up, and then this guy behind me just like whacked, not me, Nic. Just like really hit her with a program."

The situation turned ugly when Urban got into a verbal spat with the irritated opera fan, resulting in his security team escorting Urban, Kidman and her mother out of the audience, according to The Sydney Morning Herald.

Kidman was so visibly upset, someone called the police, who said they were told "a 53-year-old man and a 67-year-old man were both attending the entertainment center when an argument broke out," The Sydney Morning Herald reported.

"Violence at the opera ensued," Urban joked in the radio interview. "It was a bit of a pickle that I was in because you know, you're a husband, you want to defend your wife, but I'm like, what the hell? It took a lot of restraint."

Urban tried to reason with the man instead of getting rowdy in public.

"I think I just looked at him I said, 'It's a standing ovation,' like I didn't know I'm not allowed to (do it)," he said. "At the same time, I get it. I get that there's this thing going on where there's a traditional thing that says you don't do that. I respect that."