Neil Ferguson is known to many as Professor Lockdown. The mathematical models he created to predict the spread of Covid-19 were influential but, he says, it took him quite a long time to be persuaded that full lockdown was a good idea. A physicist by training, Neil switched from studying string theory to the spread of disease and presented scientific advice to government during the BSE crisis, an outbreak of foot and mouth disease in livestock in 2001 and the swine flu pandemic of 2009. In January 2020, he issued his first report on Covid-19 estimating the extent of the outbreak in Wuhan City in China. In March, he predicted that 510,000 people in the UK could die if nothing was done to mitigate the spread of this pandemic. Does he stand by that prediction? And how worried is he now? Jim Al-Khalili talks to Neil Ferguson about his life and work, the tricky relationship between politics and science and asks if he has any regrets about lockdown.