Yes, La Tritesse Durera was the acoustic one tonight, although James originally intended to play Masses Against the Classes. He started playing the chords from the verse and mixing it up with the high notes from the start of Faster, calling it a mash up! The crowd were very vocal shouting out requests and James messed up the start of the lyrics and stopped. The crowd convinced him to play La Tristesse and he said he'd need help with the lyrics. It was unrehearsed but really got the crowd going, cheering him on as he tried to remember the guitar solo! Nicky praised him afterwards for pulling it off and when James got his electric guitar back before the start of Sweet Child of Mine he played part of the solo again, joking that he could remember it now.
EDITED TO ADD A LINK TO A VIDEO:
https://www.youtube.com/watch?v=UpOm9RHB5rs