This may seem like an odd question — after all, he’s won — but it opens up some deep philosophical issues surrounding probability. David Spiegelhalter investigates how probability can be defined.

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In the light of recent events, it may appear that attempting to model the behaviour of financial markets is an impossible task. However, there are mathematical models of financial processes that, when applied correctly, have proved remarkably effective. Angus Brown looks at one of these, a simple model for option pricing, and explains how it takes us on the road to the famous Black-Scholes equation of financial mathematics, which won its discoverers the 1997 Nobel Prize in Economics.