The data are not available in the format requested.
It is the National Offender Management Service's policy for all prison visitors found in possession of illicit drugs to be referred to the police. As a result of which in 2007-08 the police made 424 arrests of prison visitors the majority of which would have been for drug offences.
These figures have been drawn from administrative data systems. Although care is taken when processing and analysing the returns, the detail collected is subject to the inaccuracies inherent in any large scale recording system. The data are not subject to audit.