Emma Willis hosts the second Knockout round, as 12 acts perform for a place in the live semi-final. Coaches Will.i.am, Tom Jones, Olly Murs and Meghan Trainor are in the red chairs as the acts they have chosen from the blind auditions and the Battle Rounds fight for a place on their coach's team.

Will.i.am introduces some of the highlights of the past four series, recalling some of the performances in the Blind Auditions that got the coaches' chairs in a spin, as well as memorable moments from the Battle and Knockout rounds.