LONDON: Outside supermarkets or in festival crowds, millions are now having their features scanned by real-time facial-recognition systems in the UK — the only European country to deploy the technology on a large scale. At London’s Notting Hill Carnival, where two million people are expected to celebrate Afro-Caribbean culture over Sunday and Monday, facial-recognition cameras are being deployed near entrances and exits.

LONDON: Outside supermarkets or in festival crowds, millions are now having their features scanned by real-time facial-recognition systems in the UK — the only European country to…

Britain has become the only country in Europe to deploy real-time facial recognition on a large scale, with millions scanned outside supermarkets and at...