IT is one of the most heart-rending things you will hear on radio all year. One man, talking about his late mum, in front of an audience in London's Somerset House, for 15 minutes. At times his voice broke with emotion. Many people listening at home were in tears.

"Some of the best radio I have heard for a long time," one of his followers on Twitter observed the following day. "Incredibly powerful and moving", wrote another.

In his Fore Thought broadcast on Radio 4 Tommy Whitelaw spoke about how his beloved mum, Joan, contracted vascular dementia, and how, for more than five years, he cared for her at her Glasgow home.

Tommy had worked for years in the music business, touring the world with rock and pop stars – U2, The Spice Girls, Kylie – selling official merchandise at concerts. In 2007, disillusioned and burnt out, he returned to his old Glasgow home, and to his widowed mum.

He had, however, already learned about changes in her behaviour, changes that would become much more pronounced over the next few years.

Tommy had initially planned to stay for three months, but those three months became a year. "Within that year my mum was diagnosed with vascular dementia," he said. "A really lonely diagnosis that set the theme and the standard for much of which lay ahead. With neither of us quite understanding what was happening within, around and beside us, and both becoming isolated from the lives we used to know."

Joan's friends no longer rang her or dropped by. It was, Tommy added, "two of us, becoming lost, lonely and scared."

That first year, his mum would write her name on her arm, to remind herself who she was. In her pockets, underneath her pillow, he would find scraps of paper on which she had written his name, to remind herself who this other person in her home was. "There were two of us, walking towards the crisis of our lives," he told his audience.

Over the next couple of years, Joan's dementia took increasing hold of her. But it also began to define her, in other's eyes: "Oh, that's the wee woman with dementia."

Tommy loved and adored his mum, and he became her full-time carer, but it took its toll on him, for reasons that are not hard to understand. Come the third year, he would wake up most mornings and put the quilt back over his head, and weep for half an hour. How can we get through this?, he would ask himself. "How can I keep my mum recognised as Joan Whitelaw first and never as 'dementia' first?"

Both mum and son were left helpless and hopeless. Tommy tried to seek help for her but it proved to be a soul-destroying process. He began to write a blog to see how other carers managed, and promised that if he could get a week's respite he would walk around Scotland to reach out to them.

It was a turning-point for him. He did that walk around Scotland, and addressed MSPs at Holyrood. Hundreds and hundreds of carers contacted him. “Every single letter I have received is about love … but that word is out-matched and out-numbered …by the word ‘loneliness’, the word‘isolation’," he said on radio.

“But the other thing that stands out is people. It’s people that change lives. Over and above policies and strategies, it’s people that make a difference.”

Eventually, a GP arranged for a district nurse to visit Joan. By that time Tommy was exhausted and emotionally on his knees. Joan was doubly incontinent. The district nurse fortified Tommy with her opening words then, at the end of her visit, she said "the most beautiful thing I have ever heard" – she promised to visit every Friday morning to see how they were doing.

"She is one of the reasons that I think every one of us can make a difference," said Tommy. "If I saw that nurse today I'd cross the street and shake her hand."

Joan passed away in September 2012, by which time she could no longer walk, or talk, or swallow. She had long passed the point where she could recognise the son who was holding her hand. Now, in 2016, Tommy is making it his life's work to achieve more support and respect for people living with dementia.

The recipient of many awards for his work, he is Project Engagement Lead, Dementia Carer Voices (DCV), with the Glasgow-based ALLIANCE.

DCV's You Can Make a Difference campaign has gathered pledges from health and social care professionals and students thanks to Tommy's remarkable dedication. Over the years he has given more than 500 talks and engaged with 60,000 people.

The campaign offers carers of people with dementia a chance to have their stories told, and encourages participants to reflect on what they have learnt and pledge how they can make a difference to the lives of dementia patients people and their carers.

"The response has to the BBC programme been phenomenal," he told the Sunday Herald last Thursday as he headed to his latest event, in Paris. "I've lost count of the messages of support I've received.

"Ultimately, I want to see people with dementia to be allowed to live well and die well. We want to change the conversation we have with them and their carers from 'What's the matter with you?' to 'What matters to you?' and ‘What information do you need?’ We have to do this is we are going to make a difference to each other."

He has certainly made a lasting impact. His mum has, too. In Birmingham's Heartlands Hospital, there's a reminiscence room for dementia patients and their carers. Its name is the Joan Whitelaw Reminiscence Room.

* Websites: http://tommy-on-tour-2011.blogspot.co.uk; www.dementiacarervoices.wordpress.com. The Four Thought programme is available on BBC iPlayer Radio