WATCH HERE
The live show will last 7 hours or so, starting from 7pm GMT/2pm ET.
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Guests: Jerry Springer, Simon Cowell, Piers Morgan, Scott Mills, Louis Walsh, Nicole Scherzinger, Robbie Williams, Khloe Kardashian, McFly, Michael Buble, Novak Djokovic, Julian Bunetta, Kelly Rowland, The Muppets, James Corden, Cesc Fabregas, Andy Murray, Ryan Giggs, etc.
The boys will tune in live to Xtra Factor (X Factor UK spin-off show that airs tonight after X Factor on ITV 2).
