In the early days of the COVID-19 pandemic there was a lot of confusion, as we all tried to figure out what we should and shouldn't do to best protect ourselves and others. Fortunately, we now have more definitive answers to some of our most pressing questions - which are backed-up by data - including "umm...should I be wearing a mask?". As COVID cases are again on the rise across Europe, this is the question we're putting to demographer and behavioural scientist Prof Melinda Mills.