BBC to show last days of Iris Murdoch

Thin-faced and pale, she perches uneasily on a chair and stares off camera with a mixture of child-like awe and bewilderment. Previously unseen footage reveals how in her last months Dame Iris Murdoch's brilliant mind was so ravaged by Alzheimer's disease she had no recollection of her achievements.

A home video extract uncovered by a TV documentary crew shows how the Booker Prize-winning author lost all memory of her literary triumphs as she succumbed to the debilitating condition that eventually led to her death.

The footage, to be shown in a forthcoming BBC1 Omnibus about the writer, has come to light days before the release of Iris, the critically acclaimed film of her life story, for which Dame Judi Dench has been nominated for a Golden Globe.

Shot in 1997 at the Oxford home Murdoch shared with her husband, Professor John Bayley, the video extract is taken from an interview carried out by eminent neurologist Professor John Hodges.

He asks the author whether she can remember how many books she wrote or which awards she won. But despite trying to guide her thoughts with leading comments and well-timed prompts, he is unable to stimulate her into any signs of genuine recollection.

Asked how many books she has to her name, Murdoch, whose prolific output included 26 novels and five volumes of philosophy, looks perplexed, before replying: "Of what?" Only when Prof essor Hodges specifies that he is talking about her own literary achievements, and reminds her that she has written "a lot" does she answer, "Yes."

The author demonstrates similar confusion when asked if she can recall winning any awards. After initially saying emphatically "well yes," she adds uncertainly: "Well, I can't remember ..."

Prompted to recall which of her many books won the Booker, she clearly has no recollection of the triumph of The Sea, The Sea in 1978. Shaking her head slowly, she answers simply: "No."

Professor Hodges, who runs the specialist memory clinic at Addenbrookes Hospital, Cambridge, explains in the film how he contacted Professor Bayley about visiting Murdoch after reading in a newspaper that she had writer's block. Intrigued by the way her symptoms were described in the article, he felt that they sounded more like classic signs of incipient Alzheimer's disease.

As she was renowned for her prodigious intelligence and mental alertness, Professor Hodges also half-expected to find that she had developed an unusual strain of the disease, though in the event it turned out to be standard.

"It was very sad and poignant to see someone who had obviously been a great intellect with fairly typical Alzheimer's disease."

Recalling his wife's death three years ago at the age of 79, Professor Bayley tells the documentary of the pain he felt on being parted from her. "It's a feeling one does get when somebody you've been so close to for so long just goes. You just want to go with them," he said.

Professor Bayley, whose memoirs about his 43-year marriage provided the inspiration for Iris, also recalls his late wife displaying flashes of apparent revelation in her final months. In an echo of the closing line of her last novel, Jackson's Dilemma – "I have come to a place where there is no road" – he said she once turned to him and said she had entered "a darkened room".

These moments of re-awakening are also recalled by family friend, Audi Villers whom Professor Bayley later married. She described how, while on holiday in Wales, the author suddenly exclaimed: "I wrote!"

'Iris Murdoch: Strange Love' is on BBC1 on Wednesday 23 January at 10.35pm.