The new measures are being provided through the Serious Crime Act, and as long as there is evidence linking a phone number to a prison mobile, officers and other government officials can apply for a Telecommunications Restriction Order (TRO). Should that be granted, the appropriate network will be obliged to block the device, rendering it useless.

This power, the government says, will cut down on crime being orchestrated from within prisons without the need for complex blocking technology. Earlier this year, the first official confirmation that sophisticated Stingray tracking devices were being used in the UK came from the Scottish Prison Service, not that they were proving particularly effective in blocking mobile traffic.

One thing the government has neglected to mention is how officers are expected to go about gathering the evidence they need to apply for a TRO. It sounds like the type of information that may crop up as part of a targeted investigation of someone on the outside. Not a daily occurrence, in other words, though apparently prisons "already use a number of covert techniques to identify which devices are being used within an institution."

This article has been edited to clarify that the mobile phones themselves will be rendered useless by carriers, not just the SIMs within.