And listening, too!

Police and councils are considering monitoring conversations in the street using high-powered microphones attached to CCTV cameras.

The microphones can detect conversations 100 yards away and record aggressive exchanges before they become violent.

The equipment can pick up aggressive tones on the basis of 12 factors, including decibel level, pitch and the speed at which words are spoken. Background noise is filtered out, enabling the camera to focus on specific conversations in public places.

In Holland more than 300 of the cameras have been fitted in Groningen, Utrecht and Rotterdam. Locations include city centres, benefit offices, jails, and even T-Mobile shops. The sensitivity of the microphones is adjusted to suit the situation.

Police and local council officials are still assessing their impact on crime, although in an initial six-week trial in Groningen last year the cameras raised 70 genuine alarms, resulting in four arrests.

Graeme Gerrard, chairman of the chief police officers’ video and CCTV working group, said: “In the UK this is a new step. Clearly there is somebody or something monitoring people speaking in the street, and before we were to engage in that technology there would be a number of legal obstacles.

“We would need to have a debate as to whether or not this is something the public think would be a reasonable use of the technology. The other issue is around the capacity of the police service to deal with this.”

Britain has more than 4 million CCTV cameras. The average person is filmed more than 300 times a day. The bar is being raised higher and higher — is this surveillance exclusively for criminals and terrorists? How do you prevent misuse and abuse?

How soon will it be common here?

Thanks, Joshua.