Contributor(s): Professor Sir David Spiegelhalter | Chance, luck, and ignorance; how to put our uncertainty into numbers. We all have to live with uncertainty about what is going to happen, what has happened, and why things turned out how they did. We attribute good and bad events as "due to chance", label people as "lucky", and (sometimes) admit our ignorance. David Spiegelhalter will show how to use the theory of probability to take apart all these ideas, and demonstrate how you can put numbers on your ignorance, and then measure how good those numbers are. Along the way we will look at three types of luck, and judge whether Derren Brown was lucky or unlucky when he was filmed flipping ten heads in a row.