HMP Belmarsh is 'operated' by HM Prison Service HMP Thameside is 'operated' by Serco.
HMP Thameside is a local category B prison in South East London that holds up to 1,232 convicted and remanded men. The prison is operated by Serco and is situated next to HMP Belmarsh and HMP Isis. Oxleas NHS Foundation Trust is the health provider at HMP Thameside.