Rowling said Dumbledore fell in love with the charming wizard Gellert Grindelwald but when Grindelwald turned out to be more interested in the dark arts than good, Dumbledore was "terribly let down" and went on to destroy his rival.
That love, she said, was Dumbledore's "great tragedy".
"Falling in love can blind us to an extent," she said.
The audience reportedly fell silent after the admission -- then erupted into applause.
Now ain't that a shocker? Or had you guessed it all along?