I asked my husband, Tony, to give up smoking marijuana before we moved to Cavan. It was 2003, and he had indulged in the habit for decades. We were moving to quite an isolated area, and my nagging campaign included the wish that we not give questionable individuals an excuse to turn up our doorstep.

The questionable people turned up anyway. One day a large black car pulled into the driveway. Three sharp-suited men, dressed like extras from Reservoir Dogs, got out and asked whether I knew where a certain person lived. I didn't, and they left. Later, a neighbour told me our visitors were probably Belfast drug dealers. The man they were asking for was known to have got on the wrong side of them.

But it wasn’t these gentlemen I should have been afraid of. When crisis came calling it came not from outside the family but from within. Tony’s years of smoking dope were to have a far more worrying impact on our lives. Unfortunately, they helped to mask the early symptoms of his Alzheimer’s disease.

We had moved from England, where Tony was a well-known actor. During our time in Ireland I wrote a column for The Irish Times.

Actors can be odd, egotistical creatures. I can say with some authority that they would appear, for a good deal of time, to inhabit a parallel universe; inevitable, perhaps, given that they spend their professional lives pretending to be someone else. This behaviour can spill into their private life, making it harder to understand what is mere eccentricity and what are the warning signals of something potentially more serious.

For quite a time I assumed that some of the increasing strangeness of Tony’s behaviour, such as leaving things in peculiar places or forgetting what I had just told him, was simply normal, if exaggerated, male behaviour. I researched the subject and learned that his dope habit would not have helped his memory. On that basis I thought his mood swings and occasional verbal aggression, though not at that point particularly trying, were probably part of the process of giving up the drug.

Tony has always been, and continues to be, a voracious reader. When I realised he was sometimes having difficulty differentiating between fact and fiction, I understood things were more problematic than I first realised. Sometimes he would start a conversation with me that I was completely unable to follow until it became obvious he was talking about what he was reading as if it were part of our everyday reality.

By the middle of 2004 I was concerned enough to want to get him checked out. The crucial problem was how I was going to get him to visit the doctor. I knew he would be offended and angry if I even mentioned it.

I opted for subterfuge. I had a chat with our GP, explaining my concerns, and asked if he would call Tony in for a routine health check. I requested that part of the health check should be a referral for memory testing. I persuaded Tony the referral was part of a marvellous care package the Irish health system offered to the over-70s. He was deeply impressed by this forward-thinking strategy and, believing the test was offered to everyone, agreed to go.

After several trips to the psychologist in Sligo we were told Tony was displaying clear indications of the onset of Alzheimer’s. As I anticipated, Tony was angry and rejected the diagnosis completely – an entirely reasonable response. No one wants to hear they have a life-changing illness.

Alzheimer’s is a cruel disease. As an actor, he found the thought of losing his short-term memory unbearable. How would he be able to work? Tony has always been an actor. He never wanted to do or to be anything else. He has appeared in many films, television programmes and theatre productions.

Tony’s working life spanned more than 50 years, and he was adamant that no one, including his agent, should know of his illness. He was determined to carry on working. I think he believed that by shutting the news out and employing sheer force of will he would delay or even prevent the inevitable.

While we were living in Ireland, and for some time after our return to England, in late 2005, Tony’s symptoms did not seem to get much worse. He was able to work. Although he found it harder to remember his lines, he was getting through.

Then, quite unexpectedly, he told me he could not do it any more. He was finding the physical and mental strain too much.

I know this admission came at a huge personal cost: his sense of himself is so bound up in his work as an actor. The Alzheimer’s was beginning to take this away from him.

I persuaded him once again to visit the doctor, this time on the basis that there might be a drug that would help his memory. He was told he would need a brain scan, and an appointment was made. On the day he refused to go, angry at the idea of there being something wrong with his brain.

Another appointment was made. This time both his daughter Cherie and I worked on him to attend. The scan revealed the Alzheimer’s was progressing. He was prescribed Aricept, or donepezil hydrochloride, which helps to treat the symptoms of the disease but cannot stop it. Tony winds up the pharmacist by calling them his doolally tablets – a flippancy that seems to offend their professional sensibilities.

Alzheimer’s does not follow a path of gradual decline. There are sudden steep drops, with partial loss of everyday skills. Equally suddenly, the person reaches a plateau and the decline appears to halt. In the early days it was tempting to hope the plateau periods meant the diagnosis might be wrong. I now know this is never going to be true.

We have to make the most of the good times. This summer we spent almost three weeks in France. Tony has long had an interest – bordering on obsession – with the Cathars, the heretical medieval Christians of southern Europe. He also nurtures an abiding hatred of Simon de Montfort, the French soldier who crusaded against them. A trip to Languedoc was a key part of our travel plans.

An essential tool for any car journey we undertake is a satnav, as Tony has never been an able mapreader. On many occasions the satnav has saved our marriage, in that when things go wrong we both yell at it rather than at each other. For the journey through France I decided to change the voice on the satnav. I did not want an English woman bossing us around for the entire trip. I was certain Tony would be able to cope with only one, and that had to be me. We agreed the male Irish voice was the most acceptable. “Seán”, as we soon found ourselves referring to the satnav, was a great help.

On one journey Tony suddenly asked where his office was. I had no idea what he was talking about. “Seán,” he said. “Where is his office, and how does he know when we need him?” I pulled over to the side of the road to stare at him. This was a new technological low, even for the man who once asked me which way to turn the screwdriver in order to tighten a screw.

“Ha,” he said. “Got you!”

That is my Tony. The person who wants to make me laugh, even at his own expense. At this point in his illness, the person I married can still come through.

Now, though, we are at the stage where he cannot look after himself. Tony’s forgetfulness is now the greatest threat to his safety. He has lost much of his appetite for food. His preference would be to eat biscuits or chocolate if he were hungry, and to smoke lots of cigarettes. Without me to prepare a meal there would be no balanced diet or regularity. Tony has lost weight. Some of it is possibly down to the diminished appetite of ageing – he is 82 now – but feeding him is a challenge.

There are dark times when I feel I can no longer cope. It is hard to repeat the same answer again and again as if each time were the first response to the question.

Another hard lesson, one I still struggle with, is the futility of argument. Does it matter if he insists he was the one who emptied the dishwasher when I know perfectly well I’ve just done it? If I tell him something, and he tells me later I didn’t, it is best just to let it go.

Simple, almost nonsensical issues, but like the drip, drip of water on stone the constant repetition and tongue-biting become wearing. Explosions do occur.

Like so many people in our situation, we rely on family and close friends for help. Cherie is a constant source of support. She looks after her dad regularly, so I can have a break.

This allows me to rest and enjoy simple human pleasures I would otherwise no longer have the opportunity for, such as waking up in the morning and deciding to stay in bed and read a book, or taking off for the day to spend time with friends.

I am sure everyone living with an Alzheimer’s sufferer understands the importance of respite, so you can continue to care for and support them. You cannot allow love and patience to wear out completely.

Tony is as well known for being an activist in the British Labour Party as he is for being an actor. His left-wing beliefs have not always endeared him to everyone. Once, getting into a taxi in London, the driver was perfectly friendly until he saw Tony getting in after me. He ordered us both out, as he was not having “that bleeding commie” in his cab.

After becoming a pensioner himself Tony began to channel some of his political energy into the pensioners' movement in the UK, speaking at rallies and conferences. His activities were sometimes an intense irritation to his son-in-law, Tony Blair, who was then the British prime minister. My Tony wasted no opportunity to inform the other Tony just how poor the provision for pensioners was in the UK and how much better it was in Ireland, urging the prime minister to do better.

When Tony and I discussed if I should write this piece he was initially uncertain. “It would leave me standing naked,” he said. Then, after some reflection, he told me I should do it.

Tony views his coming out as an Alzheimer’s sufferer to be the logical conclusion to his campaign for the rights and wellbeing of pensioners, although we do understand this illness can affect much younger people.

Before Tony’s diagnosis I had not really thought about Alzheimer’s. When I was a child, cancer was talked about in whispers. It was perceived as something almost shameful. Thank goodness, we have come a long way since those days.

Cancer is still a fear and a life-threatening illness for many people, but recovery rates and life expectancy have improved. There is also a greater understanding of the needs not just of the sufferer but also of families and carers. I have witnessed family and friends go through cancer. Alzheimer’s, however, is a whole new ball game.

Statistics published by the Alzheimer’s Society in the UK and the Alzheimer’s Society in Ireland make disturbing reading. Eighty thousand people in the UK live with Alzheimer’s – a figure projected to surpass a million by 2021. In Ireland 41,700 people have Alzheimer’s. The number is predicted to reach 147,000 by 2041.

The government of the UK, like those of France and other European countries, has published a national dementia strategy, designed to offer pathways to care and support. Ireland does not, as yet, have a national strategy, although the Government has committed to publishing one by the end of this year.

No one would ever suggest that funding for cancer be cut. It is time to push for comparable funding for research into the causes of Alzheimer’s disease and into appropriate care of people who suffer from it.

This disease cuts across national boundaries. Alzheimer’s can affect anyone from any background. With an increasingly ageing population, the economic burden and personal suffering can only increase. Raising awareness is crucial and overdue.

For me, this article is a milestone on our own journey. It is the first time Tony has articulated his acceptance of his illness. But Tony, being Tony, managed to rather ruin the heroic moment by saying he also wanted to tell people that his wife is writing for The Irish Times again.