I was not surprised that police forces are buying this system, but at its capabilities.

Britain’s largest police force is operating covert surveillance technology that can masquerade as a mobile phone network, transmitting a signal that allows authorities to shut off phones remotely, intercept communications and gather data about thousands of users in a targeted area.

The surveillance system has been procured by the Metropolitan police from Leeds-based company Datong plc, which counts the US Secret Service, the Ministry of Defence and regimes in the Middle East among its customers. Strictly classified under government protocol as “Listed X”, it can emit a signal over an area of up to an estimated 10 sq km, forcing hundreds of mobile phones per minute to release their unique IMSI and IMEI identity codes, which can be used to track a person’s movements in real time.

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Datong’s website says its products are designed to provide law enforcement, military, security agencies and special forces with the means to “gather early intelligence in order to identify and anticipate threat and illegal activity before it can be deployed”.

The company’s systems, showcased at the DSEi arms fair in east London last month, allow authorities to intercept SMS messages and phone calls by secretly duping mobile phones within range into operating on a false network, where they can be subjected to “intelligent denial of service”. This function is designed to cut off a phone used as a trigger for an explosive device.

A transceiver around the size of a suitcase can be placed in a vehicle or at another static location and operated remotely by officers wirelessly. Datong also offers clandestine portable transceivers with “covered antennae options available”. Datong sells its products to nearly 40 countries around the world, including in Eastern Europe, South America, the Middle East and Asia Pacific.