Trying to work out the real time incidence of a disease in the middle of pandemic has never been done before, but the team behind the ONS COVID-19 Infection Survey have developed a way to do just that.

What's the integral of x^k? If you're up to speed with your calculus, you can probably rattle the answer off by heart. But can you prove it? Chris Sangwin introduces an ingenious method for deriving the integral from first principles.