The turnaround came, they said, during a landmark high court action brought against the National Institute for Health and Clinical Excellence.

The Government’s watchdog has been criticised for refusing to allow drugs that can inhibit the early symptoms of dementia to be routinely prescribed on the NHS.

The Alzheimer’s Society says this “rationing is disgusting”.

The U-turn came yesterday, the last day of a judicial review, when Mr Nigel Giffin, a QC for Nice, conceded that doctors “must accept the general approach of the guidance”, but could decide when it was “clinically appropriate to prescribe the drug”.

The drugs demanded are Aricept (donepezil), Reminyl (galantamine) and Exelon (rivastigmine), and the case was brought by Eisai, the Japanese manufacturers of Aricept.

 “Neil Hunt, chief executive of the Alzheimer’s Society, said: “This week has been a turning point in our campaign for fair access to Alzheimer’s drug treatments.

“Finally an independent and public body has listened.”

David Pannick QC asked for a judgment spelling out the position fully. A decision is expected in weeks from Mrs Justice Dobbs.

“Later a spokesman for Nice said: “The statement referred to is not a concession, it is simply an explanation of our guidance.”