Hundreds of thousands more patients in the early stages of Alzheimer's disease could get drug treatments following a U-turn by the health watchdog.
The National Institute for Health and Clinical Excellence, covering England and Wales, now says evidence backs the use of drugs for "mild" symptoms.
Current rules prevent NHS doctors prescribing donepezil, galantamine and rivastigmine in such early cases.
Campaigners said the release of the new draft guidance was a "momentous day".
As many as 465,000 people in the UK have Alzheimer's disease, and this is expected to rise as the population ages.
The availability of drugs for the condition on the NHS has been source of controversy for almost a decade.
While there has always been evidence they diminished the symptoms and boosted quality of life for some, it has not always been clear exactly how much improvement they could deliver, to which groups of patients, and for how long.
In 2005, drugs watchdog The National Institute for Health and Clinical Excellence (NICE) ruled that no-one should get the drugs on the NHS, then conceded a year later that patients with "moderate" disease should receive them, while still ruling out "mild" patients.
The secret formula used by NICE to calculate how much "value for money" the drugs offer to the NHS was then the subject of a court action by the Alzheimer's Society and pharmaceutical companies.
After the case went all the way to the House of Lords, NICE was forced to first disclose the formula, then amend it after admitting "technical inaccuracies", although it said this did not change the outcome.
That new review now proposes giving the drugs to patients with mild symptoms - which covers people in the early stages of the disease, perhaps suffering memory loss and confusion, but not yet dependent on carers for day-to-day activities.
It has also suggested a fourth drug, Ebixa, be made available for the first time to patients with more advanced disease.
The guidance is subject to appeal.
Chief Executive of NICE, Sir Andrew Dillon, said: "Clinical trials have continued to show the positive effect of these drugs.
"Our increased confidence in the benefits and costs associated with the use of the three drugs for treating mild and moderate stages of the disease has enabled us to make positive recommendation for their use in mild disease."
He later told BBC Radio 4's Today programme it would "be lovely" if NICE had "perfect knowledge" of all the drugs it assessed from the start, but insisted the original decision had been the best they could make, based on the knowledge that was available.
"In 2007 we were not confident, and now we are," he said.
NICE's equivalent in Scotland has indicated that it may follow the guidance for England and Wales.
Ann Johnson was diagnosed with Alzheimer's five years ago, at the age of 52, and began taking one of the drugs.
"It made me become alert again and that gave me my life back."
She told Today she was "distressed" when she heard the treatment would no longer be available on the NHS, adding: "Quality of life is so important".
Ruth Sutherland, the interim chief executive of the Alzheimer's Society, said that it was "a momentous day", with approximately half of the 62,000 people who develop the disease every year likely to benefit from the drugs.
She said that the drugs, which cost approximately £2.80 per person per day, were not a "miracle cure", but made important differences to people's lives.
She said: "For the price of a cup of coffee they can mean the difference between recognising your loved ones and playing with your grandchildren.
"It is critical that this draft decision becomes a reality and that all people with Alzheimer's are given the opportunity to benefit."
The society's Director of Research, Professor Clive Ballard, said: "If this guidance is issued, doctors will no longer have to watch people deteriorate without being able to treat them."
The drugs "don't work for everybody" and have to be tried out by doctors, patients and their carers to see if they are making a difference, said Dr Marie Janson from the Alzheimer's Research Trust.
"But they can prove very valuable in the day-to-day functioning for people, helping them with that extra support for memory, concentration and attention span," she added.
Professor Roy Jones, from the Research Institute for the Care of Older People in Bath, described the decision as "an important milestone".
He said: "Early diagnosis and access to medication is critical to help reduce both the short and long-term impact of this devastating condition on patients, families and carers."