At the end of October 2007, there were an estimated 370 adult offenders (aged 21 and over) and 180 young adult offenders (aged 18 to 20) detained in Chelmsford prison. These figures exclude individuals on remand awaiting trial.
Information on the total number of prisoners in all prison establishments in England and Wales can be found at the website:
http://www.justice.gov.uk/docs/population-in-custody-oct07.pdf
These figures have been drawn from administrative IT systems, which, as with any large-scale recording system, are subject to possible errors with data entry and processing.