A team of investigators led by the World Health Organization visited a virus research laboratory in China's central city of Wuhan and met with a prominent virologist there in its search for clues to the origins of the Covid-19 pandemic.

The experts spent about three-and-a-half hours at the heavily-guarded Wuhan Institute of Virology (photo, above), which has been at the centre of some conspiracy theories that claim a laboratory leak caused the city's first coronavirus outbreak at the end of 2019...