Information on a prisoner's residence is provided by prisoners on reception into prison and recorded on the central IT system. However this information is stored in such a way that the retrieval and processing required to answer this question would be at disproportionate cost.
Work is currently under way to improve prisoner data systems and once this work is complete data will be easily obtainable and will readily be able to provide a population breakdown down to the Streatham constituency level.
It is anticipated that this work will be completed in approximately three months time and I will write to the hon. Member as soon as the data are available.