The British have long become used to video surveillance, with one of the highest densities of CCTV cameras in the world. Cameras have been used in public spaces for decades by security forces fighting threats from the Irish Republican Army and, more recently, domestic terror attacks after Sept. 11, 2001.

The recent advances in surveillance technology mean a new wave of facial recognition systems will put the public's acceptance to the test.
South Wales police have taken the lead in Britain. In 2017 they started rolling out and testing face scanning cameras after getting a government funding grant. While a court last year ruled the force's trial is lawful, regulators and lawmakers have yet to draw up statutory rules on its use.

The van-mounted cameras, using technology by Japan’s NEC, scan faces in crowds and match them up with a “watchlist,” a database mainly of people wanted for or suspected of a crime. If the system flags up someone passing by, officers stop that person to investigate further, according to the force’s website.

Rights groups say this kind of monitoring raises worries about privacy, consent, algorithmic accuracy, and questions about about how faces are added to watchlists.

It’s “an alarming example of overpolicing,” said Silkie Carlo, director of privacy campaign group Big Brother Watch. “We're deeply concerned about the undemocratic nature of it. This is a very controversial technology which has no explicit basis in law.”
Her group has scrutinized other British police trials, including one by the London Metropolitan force last year, when officers pulled aside a man who tried to hide his face. They ended up fining him for a public order offence , the group said.
The North Wales police commissioner, Arfon Jones, said using facial recognition to take pictures of soccer fans was a “fishing expedition." He also raised concerns about false positives.

British police and crime commissioners are civilians elected to oversee and scrutinize the country’s dozens of forces. They were introduced in 2012 to improve accountability.
“I’m uncomfortable at this creeping interference with our privacy,” Jones, himself a former police officer, said in an interview. He said police would be more justified using it if they had intelligence about a specific threat like an impending terrorist attack.