Star Wars Celebration 2017 wrought many interesting answers and many questions too. However, the Ian Mcdiarmid panel was laden with many answers and fascinating insight. None more so than the confirmation that Palpatine did indeed throw the duel with Mace Windu. From 31:25, we hear the question being posed and Ian's answer: (skip to 31:25 onwards) And also, a massive cheer for, Ian Mcdiarmid. Always a pleasure!