A doting Ashford father who watched his little boy beat leukaemia has died in agony from a mystery illness.

Toby Whitesman, of Imperial Way, Singleton, stayed at his son Joshua's side for more than three years after he was diagnosed with the cancer when he was only 18 months old.

But shortly after the youngster went into remission, his 38-year-old father collapsed while out jogging and never recovered.

He died at home less than three years later with his wife and two children by his side, leaving doctors baffled as to what caused the crippling illness that left the previously fit and healthy man bedridden.

Speaking at an inquest in Folkestone, wife Philippa Whitesman said: "At the beginning he was very healthy and into fitness and exercise. He'd cycle or run 15 to 20 miles a day and do abdominal work.

"He started getting stomach cramps about six years into knowing him, but that never stopped him doing anything. He went out running one day and collapsed in the street. That was the start of him going downhill."

Mrs Whitesman, who had been married to Toby for nearly 10 years, added: "He was on morphine constantly for the pain. He'd been on it for about two years. In the end it hurt him too much to even stand up.

"On the day he died his breathing was really shallow. He took one really deep breath, like a sigh. I called the children in and said: 'I think he's going.' They came to say goodbye. I think that's when he passed away."

Mr Whitesman, who also leaves Joshua's older sister Amber, stayed at Pilgrims Hospice in Margate three times in the year before his death and nurses from the charity visited him at home.

Dr Declan Cawley, from the hospice, said they were unable to identify the cause of Mr Whitesman's pain - adding it was "frustrating, professionally".

A post-mortem revealed Mr Whitesman died on February 2, 2013, from pneumonia, which is common in people who sit or lie still for long periods.

David Rose, a toxicologist at Kent Scientific Services, said Mr Whitesman had potentially fatal levels of morphine in his blood - although admitted that as the patient had been taking the drug for a long time, he might have built up a tolerance.

Mr Rose added if Mr Whitesman's last dose of morphine had been the evening before his death, as his wife believed it had been, there would not have been as much of the drug in his body as was discovered during the postmortem examination.

Mr Whitesman was diagnosed with a rare condition called sarcoidosis, which can cause painful skin and joints, tiredness and difficulty breathing but is not normally fatal.

He was also told he was suffering from a form of neuralgia – nerve pain – but was in too much agony by then to travel to hospital for further assessment, his wife told the inquest.

Coroner Rachel Redman described Mr Whitesman's inquest as an "unusual case" and said she was "mystified" by the high levels of morphine in his blood.

She added that health care professionals remained "baffled" by his symptoms.

Mrs Redman recorded an open verdict.