A highlight of the Coles’ day was always their evening meal. Oliver, a retired local government administrator, would sit down with his wife Waltraud to talk over the day’s events.

Before she was diagnosed with multiple sclerosis in 1996, Waltraud taught her native German at a university in the northeast of England. She and her husband would discuss work then watch a film, listen to one of their favourite symphonies or read in the evening.

But by last November Waltraud’s condition had deteriorated so much that this gentle ritual was transformed into a humiliating ordeal. Waltraud, 54, had lost the use of her arms and hands. Her husband was forced to spoon feed her.

Worse, after nine years, the progressive illness had left her doubly incontinent and unable to wash or feed herself. She was completely dependent on Oliver.

By the end of last year she felt her life, bedridden and weighed down by what she described as “bottomless tiredness” and “quite horrendous pain”, had become intolerable and she wanted it to end.

Too weak to take an overdose or suffocate herself without asking her husband to commit a criminal act by assisting her, Waltraud decided to starve herself to death.

On February 4 she began her self-imposed starvation, taking only a few sips of water a day. Knowing how intolerable she found her life, Oliver, 58, had no alternative but to watch her starve for 18 days until she finally died.

“I admired what she was doing. It was a courageous decision,” he says. “She had taken control and I had to admire the way she meticulously stuck to her decision. I thought that, whatever happened, her suffering was coming to an end and that it would be over in weeks rather than years.”

There are no easy answers to when someone should be allowed to die, as demonstrated by the battle between the parents and husband of Terri Schiavo, the brain-damaged woman from Florida who was finally allowed to die last week after 15 years in a vegetative state.

This week a House of Lords select committee on an assisted dying bill will publish its report into whether voluntary euthanasia should be legal in this country.

Oliver believes his wife was let down by the legal ban on assisted suicide and is continuing his wife’s campaign for a change in the law.

While he knew the starvation would, without doubt, result in the loss of his wife, he never once tried to force her to eat. “She was horrified at the idea of anything that would prolong her life,” he says.

“In a way, watching her was quite surreal. I had envisaged her resembling the starving east Africans we see on television who are no more than skin and bone, but it wasn’t like that.

“In the final stages she became extremely confused and then pneumonia set in. On her last day Waltraud slept most of the time. She died in her own home, peacefully, in her sleep, which was beyond our highest hopes.”

Because Waltraud had begun to suffer the initial symptoms of MS shortly after their marriage in 1974, the couple never had children. They were devoted to each other and spent much time discussing how Oliver would face life without her.

“I can remember Waltraud asking me how I would find coming back to an empty house and I said it would be less painful than coming into a house where my first task was to rush upstairs to see how much someone I loved had been suffering,” he says.

Two days before her starvation began Waltraud taped a statement: “People say that all life is sacred. The sort of life I now have to lead is a life I am 100% sure not a single one of these people would continue to insist is sacred and worth living if they had to live this life themselves.

“On top of this zero quality of life I now have, on top of the incontinence, on top of being spoon-fed, on top of not being able to wash myself, there also is absolutely, massively, a horrendous feeling of illness.”

After her death Oliver found a glass bottle containing his wife’s paracetamol hoard and a tape detailing her decision behind an earlier plan to take an overdose.

Waltraud had considered both suffocation and an overdose, first banishing Oliver from their home to ensure he could not be suspected of assisting in her death. But in the end she was too disabled and weak to carry out the plan. A trip to Dignitas, the euthanasia clinic in Zurich, was ruled out for the same reasons.

Deborah Annetts, chief executive of the Voluntary Euthanasia Society, says the manner of Waltraud’s death illustrates the urgent need for assisted suicide to be made legal in this country. “A lot of people will think this was a very inhumane way to secure the end of her life when an assisted, immediate death would have been a lot more dignified,” she says.

The Coles met when they were students in the late 1960s doing voluntary work decorating old people’s cottages in Brittany. Last year they celebrated their 30th wedding anniversary.

While Oliver tries to come to terms with his wife’s death he says the length and brutality of the later stages of her illness mean that, in reality, he began to grieve a long time ago. “The time when we shared a full marriage seems quite remote,” he says. “I knew I would lose her and I had a long time to mourn. More than anything I feel relieved that she was able to die in the way she wanted.”