Musical theatre singing group and winners of Series 8, Collabro, take on sword swallower Alex Magala, one of the most dangerous acts ever, Series 4 dancers Twist and Pulse, and more.

Cast: Anthony McPartlin, Declan Donnelly, Simon Cowell, Alesha Dixon, Amanda Holden, David Walliams, Vicki Barbolak, Bars & Melody, Daliso Chaponda, Collabro, Ben Hart, Alex Magala, Gennady Tkachenko-Papizh, Twist & Pulse