It is ironic that one of the things many of us missed most during 2020 was crowds. The Covid-19 pandemic meant that we were deprived of the joy and sometimes heartache of being part of crowds at matches, music festivals and other mass gatherings. The very different experience of watching football played in empty stadia across Europe has provided clear evidence of the influence of the ‘crowd’. However, the first full week of 2021 saw a dramatic reassertion of the power of the crowd by Donald Trump and his supporters in Washington, and provided a public demonstration of how crowds…