An inquest into the death of a convicted sex offender has returned a verdict of death by natural causes.

Sixty-seven-year-old James Richard Fargher was serving a four-year prison sentence for seven indecent assaults when he died from respiratory failure in Noble's Hospital last August.

The hearing was conducted in front of a jury, in addition to coroner of inquests Alastair Montgomerie, a standard procedure when a person has died while in prison.

Statements from prison governor Alison Gomme, deputy governor Colin Ring, the prison's lead nurse Bernice Ashworth and Dr Keith Wilkinson, a consultant anaesthetist at Noble's Hospital, were read out.

The jury heard Fargher had been grossly overweight and, despite suffering from diabetes, had always refused to stop eating sugary foods while in prison.

He had also refused to exercise, had poor personal hygiene and had been a smoker for a number of years.

Fargher had been diagnosed with chronic obstructive pulmonary disease on a previous admission to Noble's in 2008, while he was in custody awaiting trial.

After hearing all the evidence the jury took around 15 minutes to decide Fargher had died of natural causes, specifically respiratory failure caused by COPD.