The exact cause of death of a man who had a history of mental health problems and substance abuse remains a mystery, an inquest has heard.

Thomas O'Gregory, 48, formally known as Thomas Gardner, was found dead in his flat in Alexandria House in King's Lynn on September 3, 2018.

He had last been seen alive three days earlier.

At an inquest into his death, held at Norfolk Coroner's Court on Monday, the court heard from Pauline Gardner, Mr O'Gregory's mother, who said her son had a history of mental health problems.

She said his problems led him to spend time in various institutions: "He was struggling with mental illness which left him in a number of mental health hospitals and institutions. This was the reason he was missing from so many family photographs, he was either in hospital or prison."

Ms Gardner said after Mr O'Gregory met his wife he turned his life around, becoming a keen cook and losing weight.

But the court heard how when Mr O'Gregory's relationship with his wife broke down in May 2018, he lost his permanent accommodation and spent a period of several weeks moving between various addresses in King's Lynn and Norwich.

The court heard how despite experiencing a period of upheaval Mr O'Gregory kept in regular contact with his community mental health teams up until August 30.

But this was also heard to be a period where Mr O'Gregory started taking illicit drugs and in August entered into a relationship with a woman who was a known drug user.

Giving evidence, DS Samuel Pontin, who was called to Mr O'Gregory's flat on September 3, told the court Mr O'Gregory was found in a chair surrounded by drug paraphernalia.

He said an investigation into his death found no suspicious circumstances. A post mortem examination was also unable to determine the exact cause of death, which was given as unascertained due to the level of decomposition of Mr O'Gregory's body.

Concluding the inquest Jacqueline Lake, senior coroner for Norfolk gave an open conclusion.

She said: "The exact cause of death is not known. On the balance of probability it is not known what occurred in the period leading to Mr O'Gregory's death."