NEWS THAT THE DRUG REMBER can slow the progress of Alzheimer's will bring hope to millions. Sadly, it will be too late for my dad. The phrase "hi mate, how are you?" has taken on a special significance over recent months - it was the greeting last January that offered a rare glimpse of what he used to be like.

My dad has dementia and has been in three care homes in the past three years. Most times any of the family visit he sits, occasionally acknowledging us, but usually just fiddling with things. At his worst he appears to be in a sort of torment. The home appears good and the care assistants see to his basic needs. He is incontinent now.

Dad was always very much in control. The son of a postman, he worked as a messenger in Mount Pleasant post office in London at the age of 14. He progressed in the post office before joining the Navy in the war. At 19 he was flying a Swordfish plane on and off aircraft carriers.

After the war, he trained as a teacher, and met my mother working at a primary school. They married in 1956 and he later became head of Elmhurst School in Upton Park, London, one of the biggest primaries in the country.

Now 85, dad began to show serious signs of dementia around 2001 and it has been a gradual decline since, as he has become more withdrawn. Things got a lot worse in May 2004, followed by 18 months of rapid drift downhill until he went into the first home.

It is difficult for the family to see dad in this state. We don't know how dementia sufferers feel. They may not be in torment at all, but off in their own world where they are happy. It is something we will probably never know.

There are those feelings of duty - going to visit because you think you should, then coming out thinking "what was the point?" We wonder what is going on inside dad's head. Does he remember anything? There are those phases when dementia sufferers have greater lucidity. The "hi mate" moment was one.

It is important to support people suffering from mental illness. Around 25 million people in Britain, or 42% of the population, have a close friend or family member with dementia. It is also important that there is support for the carers. Looking after dad took its toll on my mother. She is now very nearly blind and lives alone, supported in the main by the family and local church.

The new treatment is great news that will offer hope for many, but for others sadly it is too late.

Paul Donavan is a freelance journalist specialising in social welfare issues