R is one of the most important numbers of the pandemic. But what is it? And how is it estimated? We return to the topic of testing and ask again whether the governments numbers add up. As the government encourages those who can’t work at home to return to their workplaces - we’re relying on social distancing to continue to slow the spread of the virus. But where does the rule that people should stay 2 metres apart come from? And is Vitamin D an under-appreciated weapon in the fight against Covid-19?

The question of just how dangerous Covid-19 really is, is absolutely crucial. If a large number of those who are infected go on to die, there could be dreadful consequences if we relaxed the lockdowns that have been imposed across much of the world. If the number is smaller, for many countries the worst might already be behind us.

But the frustrating thing is: we’re still not sure. So how can we work this crucial number out?

The Health Minister Matt Hancock promised the UK would carry out 100,000 coronavirus tests a day by the end of April. He claims he succeeded. Did he?

With much of the world’s population staying indoors, there are fewer cars on the roads, planes in the skies and workplaces and factories open. Will this have an impact on climate change?

Plus as the streets become quieter, is it just us, or have the birds begun to sing much more loudly?

We continue our mission to use numbers to make sense of the world - pandemic or no pandemic. Are doctors from ethnic minority backgrounds disproportionately affected by Covid-19? Was the lockdown the decisive change which caused daily deaths in the UK to start to decrease? With much of the world’s population staying indoors, we ask what impact this might have on climate change and after weeks of staring out of the window at gorgeous April sunshine, does cruel fate now doom us to a rain-drenched summer? Plus, crime is down, boasts the home secretary Priti Patel. Should we be impressed?

Many articles in the media compare countries with one another - who’s faring better or worse in the fight against coronavirus? But is this helpful - or, in fact, fair?

Tim Harford and Ruth Alexander discuss the limitations that we come across when we try to compare the numbers of Covid-19 cases and deaths in different countries; population size, density, rates of testing and how connected the country is all play a role.

John Horton Conway died in April this year at the age of 82 from Covid-19 related complications. An influential figure in mathematics, Conway’s ideas inspired generations of students around the world. We remember the man and his work with mathematician Matt Parker and Conway’s biographer Siobhan Roberts.

We compare Covid-19 rates around the world. Headlines say NHS staff are dying in large numbers, how bad is it? And is it just us, or have the birds started singing really loudly?

Scientific models disagree wildly as to what the course of the coronavirus pandemic might be. With epidemiologists at odds, Tim Harford asks if professional predictors, the superforecasters, can offer a different perspective.

(Image: Coronovirus graphic/Getty images)

Do face masks stop you getting coronavirus? You might instinctively think that covering your mouth and nose with cloth must offer protection from Covid-19. And some health authorities around the world say people should make their own masks. But expert opinion is divided. Tim Harford and Ruth Alexander unpick the arguments.