Have you ever spoken in front of a large group without a script, not entirely sure of what you were going to say?
Were you expected to talk for 5 minutes? 15 minutes? Maybe an hour? What if you were asked to speak for five hours to a group of eighty people with widely different backgrounds, from all across Europe?
What would be the worst thing that could happen? Would you stutter? Would your content completely miss the point so you would see the audience fall asleep or boo you off stage? What if, instead, you didn't provide enough material, wrapping up an hour and a half short?