Complex sentence: In 2012, Heaton was commissioned to make a large-scale sculpture,'Monument for the Unintended Performer' by Channel 4 outside its offices, to'celebrate (Channel 4's) involvement and commitment to the London 2012 Paralympic Games.
Split into simpler sentences: In 2012, he was commissioned to make the large-scale sculpture,'Monument for the Unintended Performer', by Channel 4, which is located outside its offices. It'celebrates (Channel 4's) involvement and commitment to the London 2012 Paralympic Games.