Tonight at 9pm on BBC2, the extremely moving but inspirational story of how acclaimed author Terry Pratchett is coping with the diagnosis of this devastating disease, Alzheimer’s is examined and discussed by the man himself.

Sir Terry Pratchett is 60 years old and has recently been diagnosed with early-onset Alzheimer’s disease and he’s not going to take it lying down. He wants Alzheimer’s to be sorry that it ever caught him!

As part of BBC Headroom, BBC Two’s documentary strand focusing on mental health and wellbeing, in which high-profile personalities tackle a subject matter of personal importance to them, this two-part programme sees Terry as he journeys into his uncertain future living with Alzheimer’s – a world, ultimately, without words…

Having sold almost 60 million books worldwide – and best known for his hugely popular Discworld series of comic fantasy novels – Terry is a man whose imagination is in constant overdrive. The prospect of living without memories or words frightens him: “I used to be a high-speed touch typist. I laughed in the face of the spell checker. But then, one day last year, it all started to go wrong.”

The first film begins early in 2008, soon after Terry’s diagnosis. As he battles with tying his tie and struggles to cope at a public reading of his new book, he explicitly discusses his anger at being diagnosed with an illness for which there remains no cure. The film follows Terry as he tackles the disease head on, tries out some alternative treatments and confronts leading scientists about how close they are to “the secret cure, bubbling in a cauldron”.

Surprised by how subtle the effects and symptoms of the disease actually are, Terry meets other people who share the same rare diagnosis as him, each at various stages along what he calls this “dark and unknowing path”. He visits his specialist for tests, using mini mental-state examinations to determine the severity of his condition and which parts of his brain are being affected the most. His PA, Rob, is probed to reveal more about Terry than Terry might know himself – after all, “this is the disease that hides itself even from the person who has it”.

In the second film, Terry contemplates his future and the difficulty of facing the inevitable “end game”. Terry travels across the pond to learn, first hand, how Americans are dealing with what one contributor calls the “tsunami of Alzheimer’s” that is threatening their health care, to find out if they are closer to beating the disease.

Says Terry: “If you’re diagnosed with early-onset Alzheimer’s, you feel as though you’re standing on a beach and the tide has gone out and so has everybody else. There’s no one there.”

In LA, Terry meets the unlikely doctor who has recently come across a controversial new Alzheimer’s treatment which, he claims, produces remarkable results in minutes. And in New York State he meets one of the leading experts in PCA (Posterior Cortical Atrophy), Terry’s variant form of the illness.

He confronts his probable future by visiting a care home devoted to residents with dementia, whilst evaluating the difficult dilemma thousands of carers are faced with when dealing with a loved one who can’t look after themselves.

Passionately determined to “name the demon” and rid patients of the shame and stigma attached to this illness, Terry’s desire is to find a treatment, if not a cure, which will allow him to carry on writing for as long as possible; he doesn’t have any time to waste…

The accompanying website, at bbc.co.uk/headroom, hosts a range of advice, webcasts and wellbeing guides relating to Alzheimer’s disease.

BBC Headroom has also launched a mental health action line – 08000 933 193 – which offers callers advice about where to get support if they, or someone they know, is suffering from Alzheimer’s or dealing with other mental health issues.