In Scotland Yard, London's police headquarters, there is a unit comprised of people who can recognise faces very, very well.
Xan Rice for the New Statesman — it's a long read but it's very interesting:
That August, the London riots broke out. Met officers trawled through tens of thousands of hours of CCTV footage, identifying 609 suspects responsible for looting, arson and other criminal acts. One officer, PC Gary Collins, made 180 identifications, including that of one of the most high-profile suspects, who had thrown petrol bombs at police and set cars on fire. During the riots, the man covered his mouth and nose with a bandana and pulled a beanie low over his forehead. Collins recognised him as a criminal whom he had last seen several years earlier. The man was convicted and sentenced to six years in prison.