The COVID-19 global pandemic has rapidly expanded, with the UK being one of the countries with the highest number of cases and deaths in proportion to its population. Major clinical and human behavioural measures have been taken by the UK government to control the spread of the pandemic and to support the health system. It remains unclear how exactly human mobility restrictions have affected the virus spread in the UK. This research uses driving, walking and transit real-time data to investigate the impact of government control measures on human mobility reduction, as well as the connection between trends in human-mobility and severe COVID-19 outcomes. Human mobility was observed to gradually decrease as the government was announcing more measures and it stabilized at a scale of around 80% after a lockdown was imposed. The study shows that human-mobility reduction had a significant impact on reducing COVID-19-related deaths, thus providing crucial evidence in support of such government measures. •Initial measures aimed at human-mobility reduction had a direct impact on the number of COVID-19 related deaths in the UK•Social-distancing measures may need to continue to reduce the risk of a resurgence in COVID-19 transmission in the UK•UK’s human mobility gradually decreased as measures were announced and stabilized at around 80% after lockdown was imposed•A shift in transport mode from public transport to driving was observed