The tragic Co Fermanagh couple found dead earlier this week had planned their deaths a long time ago, their son has revealed.

Dr James Barbour said his father Bill, a former grammar school teacher who was found drowned in an Enniskillen lough on Wednesday, had left a note on their back door saying the couple had “lived too long”.

Earlier Dr Barbour’s mother Ann, who was suffering from the advanced stages of Alzheimer’s disease, had been found dead at the couple’s Sligo Road home.

“My mother was diagnosed with Alzheimer’s 10 years ago. Her own mother died from Alzheimer's and I strongly suspect that my mother would have said to my father a long time ago that if she found that she had this condition he would not allow things to progress beyond a point where her dignity would have been lost,” he said.

“I suspect she might have made him make a promise. What happened was pre-determined by my mother many years ago. I think that what happened to my father was probably pre-determined some time in advance as well.

“I strongly suspect once his duty was finally done that he had no real further interest in living on without her.”

In a television interview for the BBC, Dr Barbour called for the controls surrounding euthanasia to be reviewed. Fighting back tears, he added: “Our sorrow is for the loneliness that he must have felt carrying this commitment or plan with him, not able to tell us about it for fear that we would take the matter out of his hands.

“If that was attended to then perhaps somebody carrying out the wish would have have had to do what my father did — wading into a freezing cold lake in the dark, bad weather on his own.”

Meanwhile, the post-mortem examinations into the deaths of James and Ann Barbour have been carried out. The results revealed that Mrs Barbour died of suffocation.

A spokeswoman for the Northern Ireland Coroner’s office confirmed post-mortem preliminary findings had concluded Mr Barbour drowned.

The couple, who had four children, were well-known and widely respected in the Fermanagh area having lived at their home since the 1960s.

Mr Barbour, a retired classics and Latin teacher at Portora Royal School, was a keen cyclist who dabbled in local politics as a member of the Alliance Party.

Friends have described them as inseparable and said they were often seen cycling through the town together. It is believed Mrs Barbour’s condition had deteriorated considerably in recent weeks.

And a family friend, who did not wish to be named, told the Belfast Telegraph he believed the pressure of caring for a degeneratively ill spouse would have been immense.

“It was getting to the stage where Ann may have had to go into residential care. There are homes for people with Alzheimer’s, but it is difficult for loved ones to do that.”