A baby has died at Britain’s largest female prison after an inmate reportedly gave birth alone in her cell in the first known case of its kind in modern times.

The woman, who was known by the prison to be well advanced in her pregnancy, gave birth in the early hours of Friday last week. When prison staff visited the woman’s cell on Friday morning, the baby was unresponsive.

Police are investigating and Sodexo, the private company which runs the prison HMP Bronzefield in Ashford, Middlesex, said it was conducting a review

Surrey police said in a statement: “The death is currently being treated as unexplained and an investigation is continuing to establish the full circumstances of what happened.”

The case raises serious questions about how the woman came to be unsupervised and without medical support during her labour and birth.