Newscaster John Suchet’s moving account of his wife’s dementia was meant to be cathartic.

Instead, his grief is as raw as ever.

Just eight months ago, veteran newscaster John Suchet made the agonising decision to put his wife Bonnie, who suffers from dementia, into a care home.

Since then, the former ITN broadcaster, who still visits his wife once a week, has been battling to move on. He is selling the London flat they shared for 25 years to move nearer to his brother, the actor David Suchet, and has already sold the holiday home in south-west France which they adored.

He has sent many of Bonnie’s clothes to the charity shop and has sorted through thousands of photographs.

“When I look at them I feel utterly miserable and dejected,” says John, 66. “We used to joke that we’d look at them in our old age. I can’t see a point when I’ll ever be able to look through those albums and smile.”

He is “ambushed” by little events which spark a flood of grief on a regular basis, he says.

“The classic one was walking past the charity shop on the way to the station and, wallop, in the window there was Bonnie’s stuff. Major ambush.”

He has kept himself busy to keep his grief at bay, throwing himself into charity work as the honorary president of Dementia UK, which supports Admiral Nurses who are specifically trained to help dementia sufferers and their carers.

He has also launched the Admiral Nurse Academy, an online service providing a gateway for everyone interested in Admiral Nurses and the services they provide, named “in honour of Bonnie Suchet”.

And he has written My Bonnie, their love story and an account of how dementia has taken her away from him. Only when you read it can you realise how lost he is without her.

“My family said, it must have been lovely to go back and relive those memories for the book, but I spent most of the time in tears. The truth of it is, half of me wishes I’d never written the book because it’s like an open wound that just doesn’t heal.”

The love story began 40 years ago, when they met socially as neighbours in Henley. Both were married at the time. John had three young sons and Bonnie, an American, had two. As their feelings for each other grew and cracks appeared in their marriages, they left their spouses to be together.

Bonnie joined John in America, where he was ITN’s Washington correspondent. It was clear their relationship was not just a fling.

“Our life together was idyllic from day one.

“She was the most beautiful, gentle, lovely, wonderful woman. She even saved my career, which was on the skids when we got together – I ended up with a lifetime achievement award (in 2008). She came to the event with me and it turned out to be her last public outing. How ironic is that?”

Bonnie, a former beauty queen, started to show signs that all was not well in 2004.

Her forgetfulness and confusion increased, and in 2006, she was diagnosed with dementia, aged 64.

Suchet talks about the “breakdowns” he suffered as he went from being her lover to her carer, losing his temper with her, stomping around, swearing, grabbing her by the arms until she was bruised.

“The way I behaved towards her at some moments was dreadful. I wondered if it was part of my character, that deep down I could be quite a nasty chap, or was it entirely brought on by the disease?”

He had help from an Admiral Nurse, a specialist trained to work with family carers and people with dementia.

John thought that writing the book might be cathartic, but it wasn’t. He says he spent much of his time in tears and he hasn’t coped well since Bonnie moved to the home.

Yet he looks forward to his weekly visits to Bonnie, who recognises him and is always pleased to see him.

“She calls me John, she knows I’m special. Does she know I’m her husband? I have no idea and I’m not going to ask her. You don’t put someone with dementia on the spot.”

Each time he leaves her, he feels distraught, especially as she doesn’t seem to mind.

“The other day as I was going, she saw the lift open behind me and she just walked away and didn’t say goodbye. She knew she had to stay and I had to go. And this is the woman who once said to me, ‘Whatever time you leave the flat, don’t ever leave without giving me a hug’.”

My Bonnie: How Dementia Stole The Love Of My Life, by John Suchet, is published by HarperCollins, priced £18.99.