Following the outbreak of COVID-19, a number of non-pharmaceutical interventions have been implemented to contain the spread of the pandemic. Despite the recent reduction in the number of infections and deaths in Europe, it is still unclear to which extent these governmental actions have contained the spread of the disease and reduced mortality. In this article, we estimate the effects of reduced human mobility on excess mortality using digital mobility data at the regional level in England and Wales. Specifically, we employ the Google COVID-19 Community Mobility Reports, which offer an approximation to the changes in mobility due to different social distancing measures. Considering that changes in mobility would require some time before having an effect on mortality, we analyse the relationship between excess mortality and lagged indicators of human mobility. We find a negative association between excess mortality and time spent at home, as well as a positive association with changes in outdoor mobility, after controlling for the time trend of the pandemic and regional differences. We estimate that almost 130,000 excess deaths have been averted as a result of the increased time spent at home. In addition to addressing a key scientific question, our results have important policy implications for future pandemics and a potential second wave of COVID-19.