Some excerpts:
Interesting what can be accomplished applying fairly simple tech, isn't it...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.
....
Barrister Jonathan Lennon, who specialises in cases involving covert intelligence and Ripa, said the Met's use of the Datong surveillance system raised significant legislative questions about proportionality and intrusion into privacy.
"How can a device which invades any number of people's privacy be proportionate?" he said. "There needs to be clarification on whether interception of multiple people's communications – when you can't even necessarily identify who the people are – is complaint with the act. It may be another case of the technology racing ahead of the legislation. Because if this technology now allows multiple tracking and intercept to take place at the same time, I would have thought that was not what parliament had in mind when it drafted Ripa."