How Covid-19 contact tracing can help beat the pandemic

If the UK government wants to start easing the country's lockdown restrictions, it needs to get contact tracing right. But what does that mean? What would successful contact tracing even look like? Josh Toussaint-Strauss tries to find out with a little help from Christophe Fraser, an Oxford professor and infectious disease epidemiologist, and Alex Hern, the Guardian's UK technology editor