This live facial recognition system is being tested against Christmas crowds

ZDNet 

London's police will be testing out live facial recognition technology on Christmas shoppers today and tomorrow. The Metropolitan Police Service said the test, which will cover areas in Soho, Piccadilly Circus and Leicester Square, is part of its ongoing trial of the technology. When people pass through the area covered by the cameras, their images are streamed directly to the police facial recognition system database. This database contains a watch list of offenders wanted by the police and courts for various offences. The system measures the structure of each face, including distance between eyes, nose, mouth and jaw, to create facial data.