A diabetic who received a massive overdose of insulin remained in a vegetative state for 12 years, an inquest heard.

But exactly how Carol Ann Tompsett came to overdose remains a mystery, as her relatives said she would not have been trying to kill herself.

Mrs Tompsett, 62, died on December 2 last year at the Hafod-y-Green Nursing Home in Trefnant, where she had been in a persistent vegetative state since the incident in 2005.

Her aunt, Joyce Stanley, told the inquest in Ruthin that Mrs Tompsett, a divorcee, was diagnosed as diabetic in 1991 and prescribed insulin in 1999.

She had had a troubled life, losing two children and suffering from depression, for which she received counselling.

She moved back from Hong Kong to live with her parents and was very close to her father, visiting him in a Rhyl care home every day.

Mrs Stanley said: “It’s very difficult to explain how close they were”, adding: “Carol would never have wanted to take her own life: she was dedicated to her Dad.”

In a statement her brother Noel O’Neill wrote: “She and her Dad were the best of friends. If she had wanted to kill herself she would have done it earlier.”

Mrs Stanley praised the standard of care her niece had received at Hafod-y-Green.

Mrs Tompsett died after contracting a chest infection which developed into pneumonia.

Recording a conclusion of misadventure, Joanne Lees, assistant coroner for North Wales East and Central, said: “There is no evidence that the overdose was deliberate and that she intended it to cause her death.

“It’s a very long time for a person to be in that condition.”