Around 200 patients with early Alzheimer’s are now being recruited for the trials at Addenbrooke’s Hospital in Cambridge.

It follows a landmark study led by Professor Christian Holscher at Lancaster University, which found that the drug Liraglutide -  already used in the treatment of diabetes – appeared to reduce the damage caused by dementia and result in memory improvements.

Mice with advanced Alzheimer’s given the drug performed much better on tests while their brains showed a 30 per cent reduction in the build-up of toxic plaques in the brain.

The discovery was so important the Alzheimer’s Society and other charities agreed to fund the £5million trial to test the effectiveness of the drug in people with Alzheimer’s disease.

Professor Holscher said the treatment could be on the market within five years.

“My research showed it’s potentially very effective and I think we are really on to something.

"This could be a very big advance. If these clinical trials show positive effects the next stage is a larger study.”

If the drug is found to reverse damage to the brain, or to stall disease progression, the drug could be the first treatment to prevent Alzheimer’s disease.

Alzheimer's disease is the most common cause of dementia; it is predicted there will be more than 520,000 people in the UK with the disease in 2015.

Dr Paul Edison, Clinical Senior Lecturer at Imperial College London and Consultant Physician at Hammersmith Hospital is leading the study.

“There is evidence that shows there’s a mechanism in the brain of patients with diabetes which is the same in patients with Alzheimer’s. We saw there’s about 70-80 per cent increase risk of people with diabetes getting Alzheimer’s.

If these trials are successful, Liraglutide would be the first new dementia treatment in a decade.

Dr Simon Ridley, of Alzheimer’s Research UK, said: “Clinical trials are crucial to understand whether a treatment could help people with Alzheimer’s, so it’s encouraging to see this drug taken forward.”