During a performance for operatic duo Richard and Adam Johnson, a viola player dressed in black emerged from the symphony, walked between the two singers, and began throwing eggs at Cowell from the stage, the UK's Mirror reports.
It turns out the mystery woman is Natalie Holt, who auditioned for Britain's Got Talent last season as part of a string quartet. She got five eggs off from a carton before security pulled her away. At least one of those eggs apparently connected, prompting Cowell to brush off eggshells and change out of his jacket. Holt told UK newspaper The Telegraph: "I basically took a stand against people miming on television, and against Simon and his dreadful impact on the music industry."
"I sent a tweet off yesterday that I didn't like eggs, and I really don't like eggs now," Cowell said after the Johnsons' performance, which did not stop despite the interruption. "I have no idea what that was about. So whoever is watching, I apologize."
The Johnsons did not stop singing, despite the unexpected turn of events, and commented afterward, "It's disappointing that someone tried to sabotage our performance but we're proud that we made it to the end of our song. Thanks to everyone for their support. We've had a great time."
Holt eventually issued an apology: "I want to apologize to Richard and Adam for overshadowing their performance. I've never done anything like this before and in hindsight I have realized it was a silly thing to do."
Although police were called, a rep for the show says that "we have decided to take no further action at this stage."
Watch the egging here: