But five minutes after being injected with etanercept – according to the film which was supplied and edited by the clinic – he greets his wife. Visibly shocked, she says he has not recognised her for years. Mr Miller then hugs her.

"On the surface these results are exciting but we need to treat the study with caution," she [Suzanne Sorenson, head of research at the Alzheimer's Society] said. "There are large gaps in the research, which used a small pilot group. We cannot draw conclusions until a controlled trial is carried out."