Teenager Jonathan Antoine, performing with singing partner Charlotte Jaconelli, walks on to crowd jeers and a dirty look from Simon Cowell.
However, the "shy" opera singer shocks the London audience into a standing ovation after a magnificent performance.
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Cowell attempts to break the pair up, opining that Jonathan should go alone into the next round: "OK, this is what I think - Charlotte I think you're good, but Jonathan you are unbelievable. I mean, seriously, you have an outstandingly good voice.
"I like the fact that this works as a duo but I worry Charlotte whether you're gonna hold him back."
However, 17-year-old Jonathan stands firm, insisting: "Well we've come on here as a duo and we're gonna stay here as a duo."
Fellow judge David Walliams brands the act "incredible", while Alesha Dixon describes the pair as "world class".
Watch a clip of Jonathan Antoine and Charlotte Jaconelli performing below:
Britain's Got Talent premieres tonight at 8pm on ITV1.
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Watch Simon Cowell talking to Digital Spy about the new series of Britain's Got Talent below: