Oliver James famously got in touch with Peter Mandelson's hidden emotions a few years back in a memorable television interview.

Mandelson was a guest on Dr James's television series The Chair, and when questioned by the celebrated psychologist about the death of his father, Mandy, that most image conscious of politicians, was seen to cry.

The programme was to win Dr James plaudits as a media psychiatrist who could offer glimpses of things we couldn't imagine.

True to form, his latest project aims to change the way that the world views and treats the thousands of elderly people who suffer from dementia.

He has spent most of his working life looking into how we bring up our children. But thanks to his mother-in-law, Penny Garner, he is now on a mission to show that the world needs to change its whole approach to looking after elderly people suffering from dementias, such as Alzheimer's disease.

For 18 years, at a hospital in Burford, Mrs Garner has been employing what is held up to be a groundbreaking method to end the hell of dementia.

Anyone who doubts the impact it can have, only need to recall the words of Terry Pratchett, Britain's bestselling fiction writer, when he announced he was in the early stages of the illness at the age of only 59.

Alzheimer's, he said, was "like stripping away your living self — a nasty disease, surrounded by shadows and small, largely unseen tragedies".

He envied, he said, his father's death through cancer.

But it does not have to be like that if Dr James and his mother-in-law are right.

Her revolutionary technique, it is claimed, removes the need for anti-psychotic medication and allows victims of dementia to live happy and dignified lives.

As for families and carers, it offers an escape from a neverending nightmare of frustration, anger and embarrassment.

In a bid to draw wider attention to the methods Mrs Garner has been quietly employing in west Oxfordshire, Dr James has written a new book entitled Contented Dementia: 24-hour Wraparound Care for Lifelong Well-being.

As the author of such books as Juvenile Violence in a Winner-Loser Culture, They F*** You Up and Britain on the Couch, Dr James admits: "The subject of dementia didn't interest me. The things I have written about are the impact of early childhood experiences on personality and the impact of society on the way we care for children. I'm a child clinical psychologist."

But then he met his remarkable mother-in- law.

Mrs Garner, wife of a GP, was a Cotswold housewife without a university degree when she got started nearly 20 years ago.

"The inspiration was the dementia of her mother, Dorothy," explains Dr James, who lives in the west Oxfordshire village of Idbury. "This single case taught her all the fundamental skills she needed."

She went on to develop them working with older people at the community hospital in Burford, initially as an Alzheimer's Society helper.

Through observation of what helped and what distressed the patients, she put the pieces of her theory together.

Her great revelation, he believes, has been to recognise that a great deal of the mind and emotional self of the person with dementia is still functioning as well as ever. In fact, the only difference between the person with dementia today and the person you used to know is a single disability — they can no longer store new information efficiently.

But memories from long ago remain largely undamaged and intact.

Grasping that one fact clarifies much of what the person with dementia says and does, also providing the key to unlocking their isolation and distress.

"In plain language," he tells us, "people with dementia are often using past experiences to make sense of the present. In the absence of new information, which they have not been storing, they naturally search for past situations to provide them with a context, to indicate what the hell is going on — the fundamentals such as 'who are these people around me and where is this place?'."

When her mother developed Alzheimer's, Mrs Garner well recalls them sitting together in a doctor's waiting room. Out of the blue her mother anxiously asked: "Has our flight been called yet? We don't want to miss it. Where's the hand luggage."

It was to prove a turning point, because Mrs Garner realised what was happening.

Her mother had always loved to travel and it was her mother's way of making sense of a crowded waiting room situation by assuming they were in a departure lounge.

When Mrs Garner responded, "our luggage has been checked in — we've just got our handbags", her mother visibly relaxed.

The lesson she learnt that day was that if you cease requiring dementia sufferers to store new information when talking with them, many of the problems disappear.

The secret is to stop asking questions and always agree with everything they say, never interrupting them.

But the idea of building a care plan built around a person's past experience, allowing them to live a kind of happy 'groundhog day', surely brings its own problems.

Does it not, for a start, mean consigning dementia sufferers to a 'la-la land of the past'?

Dr James argues that if a person is happier in the past, this must simply be accepted and benefits will follow.

"If the person is comfortable in the old narrative, they are much more likely to see the necessity for eating, sleeping, going to the loo and all the other vital functions that are so often problematic for carers to orchestrate."

He also forcibly argues that the alternative is to continue treating dementia sufferers with anti-psychotic medication.

Half of the 200,000 people with dementia who are living in care homes are currently taking anti-psychotic drugs. Many more living with their families are also on them.

Yet Dr James points to research that shows a quarter of the elderly pill-takers will die prematurely as a result of the side effects. As well as that, the risk of psychological damage is said to be huge, with people left befuddled and doped.

Staff at the Burford hospital were impressed by Mrs Garner's approach and the improvements to dementia sufferers who visited the day centre.

With the help of Professor Tom Kitwood, of Bradford University, she went on to create the Specialised Early Care for Alzheimer's (Specal) project. It was launched as an independent charity in 2003.

And when the NHS announced its intentions to sell Burford's hospital to bring in £800,000, she persuaded a benefactor (who has remained anonymous) to buy the hospital site for the charity to allow its work to continue.

Mrs Garner said that at the beginning of the year lack of funding forced her to make all Specal's six clinical staff redundant.

"We were forced to shut the doors at the beginning of January," she said. "But the staff involved with dementia all came back. They said they would work for nothing to try to help. So we have just kept going this year. I think we are unique in dementia care. There have been 18 years of continuous study, using the same method, in the same building, with the same patient group."

Yet it does not represent a proper medical study and if Mrs Garner hoped the new book would win universal acceptance for her methods, she will be disappointed.

A review in the Alzheimer Society's magazine finds much to admire in the book, but dismisses the idea that people with dementia can live happily by supporting their illusions as "improbable".

Graham Stokes, head of mental health at BUPA, writes: "I advise any reader to respect Penelope Garner's commitment to people with dementia, but not to be seduced by the simplicity of the model into believing that Specal is the soundtrack of person-centred care. It is just one psychosocial intervention in the therapeutic tool kit.

"The emphasis on the value of good communication, and the need to evidence base what works best is to be commended. However, Specal is not the only approach to dementia care, as Oliver James proposes."

Mr Stokes is particularly unhappy with what he calls "the commandment" that carers never ask questions, which he claims is "as poisonous to the well-being of people with dementia as radiation is to the health of newborn babies".

"Not only does this smack of disempowerment," he says, " it runs contrary to all that is enshrined within the Mental Capacity Act that supports decision-making as memory fails."

But as Dr James again returns to his work on children, while dedicating time to looking after his own two youngsters, he can reflect that his headline-making ability has made the treatment of dementia a major issue.

And he is still able to joke: "I must be the only man in Britain who would like my mother-in-law to look after me if I had dementia."