Britain's Got Talent 2015: Watch Alesha Dixon perform her new single (Semi-Final 4)

Britain's Got Talent 2015: See Stephen take a tumble (Semi-Final 4)

Britain's Got Talent 2015: Get in! Isaac Waddington and The Neales get the results (Semi-Final 4)

Britain's Got Talent 2015: Young singer Maia Gough doesn't know her own strength (Semi-Final 4)

Britain's Got Talent 2015: Are Boyband leaps and bounds ahead of the competition? (Semi-Final 4)

Britain's Got Talent 2015: Musician Isaac Waddington can't make you love him (Semi-Final 4)

Britain's Got Talent 2015: Marc Métral and Miss Wendy wow the crowd (Semi-Final 4)

Britain's Got Talent 2015: Jeffrey and Chantal reach for the stars (Semi-Final 4)

Britain's Got Talent 2015: The Neales are in perfect harmony (Semi-Final 4)

Britain's Got Talent 2015: The Kanneh-Masons perform a musical medley (Semi-Final 4)

Britain's Got Talent 2015: Lisa Sampson's playing with fire! (Semi-Final 4)

Britain's Got Talent 2015: OK WorldWide are bouncing off the walls (Semi-Final 4)

Britain's Got Talent 2015: OK WorldWide are bouncing off the walls (Semi-Final 4)