Earlier today, Prof Neil Ferguson told a parliamentary committee that the UK death toll would have been halved if the UK had locked down a week earlier. A claim certain to generate headlines – but how confident can we be in his figures? I’m a financial strategist, and like many people whose day-job is analysing complicated data I have been watching – open-mouthed – at how estimates have been dressed up as fact during this epidemic. Imperial College's hypothesis is not difficult to explain. Before lockdown, Covid was growing with a reproduction number of about 4. So: every infected person gave it to four others, each of whom gave it to four others etc. If this were the case, you don’t need to be a maths genius to see that it would spread in a terrifying way.