Of all the places in the United Kingdom, one would have expected that Her Majesty's Prisons could be kept free of illegal mobile phones.
It should be trivial for the mobile phone networks to detect any unauthorised mobile phones physically within Prisons and to alert the authorities automatically (after, no doubt, charging them a suitable Location Based Services fee). It should be technically easy to install radio triangulation equipment which spots and accurately locates a mobile phone within a Prison, as soon as it is switched on, even for a few seconds.
However, according to these figures published in Hansard, it appears that the Ministry of Justice (and the Home Office before them) are failing to prevent the smuggling of mobile phones into prisons.
They claim to have seized 3,473 mobile phones (or SIM cards) in the last year (October 2006 to September 2007)
This must also imply that there is a huge illegal drugs smuggling racket as well, and that it seems very likely that corrupt Prison Staff must be involved:
Dec 2007 : Column 1261W
Prisons: Mobile Phones
Lady Hermon: To ask the Secretary of State for Justice how many mobile telephones were seized in prisons in England and Wales in each of the last 12 months. 
Maria Eagle: Prison establishments are required to send all seized mobile telephones to HMPS Security Group for interrogation. The following table contains the number of mobile phones (which includes handsets, handsets containing SIM cards, and individual SIM cards) seized and sent for interrogation in each month from 1 October 2006 to 30 September 2007.
5 Dec 2007 : Column 1262W
Month Total number submitted for interrogation October 2006 230 November 2006 249 December 2006 178 January 2007 310 February 2007 330 March 2007 240 April 2007 272 May 2007 400 June 2007 302 July 2007 334 August 2007 333 September 2007 295 Total 3,473
We would like to see some statistics on how long it takes for these illegal mobile phones to be detected and confiscated.
The figures for each individual Prison should be also be published.
A Further Thought:
Given that modern mobile phones can also include BlueTooth and/or WiFi,then the radio security defences of Prisons should also check these methods of sending messages. An extended range antenna and/or an illegal amplifier, in a vehicle in the car park or in neighbouring streets could well penetrate the walls of the Prison, without making use of the actual mobile phone network.
Cordless DECT phone handsets might also be illegally amplified to reach in and out of a Prison.