, which was launched in April, is a free app. Users enter their postcode and will then be shown a series of CCTV images of suspects who the police wish to speak to.

"My hope is that the two-thirds of Londoners who own smartphones will download this app, and help us identify those suspects we still need to speak to," , Metropolitan Police assistant commissioner and head of specialist crime and operations.

"We need Londoners to browse through the app every week or so as new images will appear regularly. This is a fantastic way for Londoners to help us to fight crime."

Rowley assured reporters that civil liberties were properly considered when designing the app.

"The police have always used images in public appeals," he said. "So there's no change there. This is using technology to bring those appeals to a much bigger audience.