Some years ago I went to a three-day conference in Sydney where the opening keynote was given by a global academic star.
She arrived on the first morning of the conference, having flown first class from United States on a ticket paid for by the organisers. She gave a lively talk to a packed auditorium, fielded questions with aplomb and mingled charmingly with delegates at morning tea. Then as the first session of general papers was about to commence she gave her apologies and retired to the five star hotel room the organisers had booked for her to sleep off the jet lag. No more was seen of her at the conference. Late the same evening she boarded a flight to Tokyo where she would give another keynote the next day.