The Masked Singer fans became even more convinced by Fox's identity after spotting a crucial clue in her dressing room.
Tonight, Fox sang Katy Perry's Firework and wowed the judges with her singing, but equally made them even more certain that they had a musical theatre background.
As the judges speculated on who it could be, host Joel Dommett gave them a peak into her dressing room.
Inside, there were flowers and cards on the table - including one from ALW, which the judges quickly worked out must have been from Andrew Lloyd Webber.
Excited fans flocked to Twitter over the revelation, with one tweeting: "Denise was the judge on the ALW Joseph BBC show and married the winner #maskedsinger."
While another commented: "Denise Van Outen was on Over The Rainbow with Andrew Lloyd Webber. Cracked it. #MaskedSinger."
A third remarked: "Denise did Tell me on a Sunday and also judge on I'd do anything and Any dream will do with Andrew Lloyd Webber. #MaskedSinger."
"It’s DEFINITELY Denise because she judged Any Dream Will Do to find the next star for Joseph and the Amazing Technicolor Dreamcoat with Andrew Lloyd Webber #MaskedSinger," another wrote.
Another commented: "The fox is definitely Denise Van Outen -she was a judge on Any Dream Will Do with ALW (Andrew Lloyd Webber)!!! #TheMaskedSinger #maskedsingeruk #MaskedSinger."
*The Masked Singer airs Saturdays at 7pm on ITV
