AFTER more than half a century together, veteran actor Timothy West and his wife Prunella Scales are still as inseparable as ever, despite her ongoing struggles with dementia.

At their Victorian house in Wandsworth, south London, former Fawlty Towers star Prunella remains in the background while her husband discusses his latest book, Our Great Canal Journeys: A Lifetime Of Memories On Britain's Most Beautiful Waterways, a lovely coffee table tome which details their famous journeys both on the water and in life.

Viewers will have seen moments on their Great Canal Journeys Channel 4 series, where Prunella loses clarity, which has clearly struck a chord with many.

What began as a gentle, seemingly light-hearted travelogue has become something far deeper and more touching than this devoted couple could have imagined, which is evident from Timothy's accounts in the book.

They still rely on each other, their lives gloriously entwined, but Prunella's foreword reveals her frustration with what they call her 'condition'.

"I hate the idea that the world is going on all around me, but that so much of it is closed off. I soon forget my anger, though, as I forget nearly everything else.

"I think this book is a bit like one of our canal journeys; meandering along through our lives until it is suddenly carried away by a current, or a weir, or a sandbank," she writes.

Timothy, 83, whose stellar career has taken him from the Royal Shakespeare Company to Coronation Street and EastEnders, admits the canal journeys have become trickier as time has gone on but, so far, that hasn't deterred them.

"It needs much more preparation and support, but we can do it and Pru is insistent that we should," he says. "She doesn't want the alternative of sitting at home and watching daytime television.

"My daughter Juliet [from his first marriage] comes with us, officially as hairdresser, but she's her carer as well. Pru's fine. She loves doing it and likes being in the programme."

Prunella, 85, doesn't do as much of the physical work now connected with getting through difficult locks, he explains.

"As long as there's somebody to tell Pru what's going on, she's absolutely fine. She loves the wildlife and watching the ducks, herons and water voles. She always says that seeing the angle just a couple of feet above the water gives you a new insight into nature."

As for life at home, Prunella has largely given up acting, although she still does radio plays. They don't go to the theatre or cinema often because she can't remember much of it afterwards, she confesses.

Timothy counters: "We do go to the theatre but we don't go to expensive theatres very much. If only one of you can remember what it's all about, it's a bit of a waste of money.

"I miss an awful lot about our early life together," he continues, "but you mustn't think about that. We have to take each day as it comes."

Prunella remembers the canal journeys more than a lot of things, he adds.

"There's something about the country that stimulates her. People who know a lot about the condition say, 'Yes, you've got to keep going'.

"It's a way of seeing the country slowly, peacefully and from a different direction. It's a way of going from A to B but it's never going to be in a direct line."

How does he feel about the future?

"It's been difficult but it's manageable. Of course it [Prunella's dementia] is going to get worse. We both love this house and the garden and the way of life that is possible to us here, and we would like to keep that as long as possible," Timothy says. "In the meantime, with people to help, we're doing all right."

Prunella explains in the book that they don't get asked out as much as they used to, because she can't remember conversations – and Timothy admits he has to check himself at times to stop being impatient with her.

"Darling Pru is getting a little less sure of herself all the time; only a little, perhaps, but I ought to be constantly on the lookout.

"She insists on doing tricky things, because she loves it, but of course needs constant encouragement; so getting irritable with her is the worst thing I can do," he writes.

Away from the canal journeys, he's still acting, attending theatre festivals, poetry readings, charity events and appearing in TV dramas.

"Pru doesn't act now. She can do a poetry programme. We sometimes read things together in public."

For now, he doesn't have any more TV canal journeys planned, although he would like to go to the Nile and perhaps the Suez and Panama Canals.

His wife, he says, remains blessedly free of depression and distress about her condition.

"Off camera, we will now get back to our own beloved boat, in Braunston Marina, and take off for a few days, just pottering along and tying up somewhere to read a book and open a bottle of wine."

Our Great Canal Journeys: A Lifetime Of Memories On Britain's Most Beautiful Waterways by Timothy West is published by John Blake, priced £20. Available now.