The UK has introduced new rules requiring all people arriving in the country to self-isolate for 14 days. But given the severity of the UK’s outbreak can there be many places more infectious? Is it true that Covid-19 mostly kills people who would die soon anyway? The first figures are out showing how England’s Test and Trace programme is performing, but they contain a mystery we’re keen to resolve. And we play with some mathematical puzzles, courtesy of statistician Jen Rogers.