 The study evaluates the effectiveness of physical distancing policies in controlling the spread of COVID-19 in the UK. The authors conducted an online survey of UK adults to assess their contact patterns on the previous day, including age and location of contacts and intimacy of physical contact. They compared these patterns during a lockdown to patterns during a non-epidemic period and estimated the change in reproduction number, R0, as a consequence of physical distancing measures. The results showed a 74% reduction in average daily contacts observed per participant, which would reduce R0 from 2.6 prior to lockdown to 0.62 after the lockdown. The authors conclude that physical distancing measures have substantially reduced contact levels and will likely lead to a decline in cases in the coming weeks, but this projected decline may not occur immediately due to delays between infection, symptomatic disease onset, and hospitalisation. Tracking behavioural change can provide a more rapid assessment of the impact of physical distancing measures than routine epidemiological surveillance. This article was authored by Christopher I. Jarvis, Kevin Van Zandvoort, Amy Gimmer, and others. We are article.tv, links in the description below.