The Welsh crooner made an appearance on the BBC show on Thursday night, where he reflected on his marriage to his wife Linda Trenchard, who died in 2016 after being diagnosed with lung cancer.
Speaking about how songs on his latest album tell stories about different parts of his life, Tom explained how the song I Won’t Crumble With You If You Fall took him back to Linda’s final days.
He told Alex and co-host Michael Ball: “I was there in the hospital room with her for the last 10 days and I said, ‘My god Linda, I don’t know what I’m going to do with myself because I won’t be able to sing, I won’t be able to get the words out.’
“She said: ‘You must! Don’t fall with me. You know, I gotta go. But you don’t have to. And you’ve got to go and do what we planned to do’, which was to move back to London. She said: ‘I’ve just ran out of time. But you’ve got to go and do it now.’
“And she said: ‘But when you get on the stage, think of me laughing. Don’t think of me as I am now. Think of all the years we’ve had together and that should lift you up.’ Which it does.”
Tom’s personal story touched Alex, who was seen looking emotional and clutching her heart.
Tom and Linda were married for 59 years before her death in 2016.
The pair were childhood sweethearts and married when they were just 16.
Tom previously described how he cancelled the Asian leg of his tour and flew back to Los Angeles when Linda was told she had just a week to live following her diagnosis.
The One Show airs weekdays at 7pm on BBC One.