Smooth Ken in his element back working in Scotland

So how long ago is that? It's after the show and Bruce and I are sitting in a quiet makeshift green room/tent. "About 37 years," he says in a surprisingly soft spoken voice. One on one, Bruce doesn't need to make his voice heard to anyone but me.

"I started at the BBC as a staff announcer. I was going to be a serious broadcaster - and I was for a couple of years. And then the BBC said, 'You're never going to be Jeremy Paxman. What you do is take the mick.' I realised this is what I should be doing and god bless the BBC for deciding it. I've been getting away with it ever since."

You could say that: Bruce's audience figures now top an astounding eight million, a wonderful "validation" at his age, he says; although he doesn't keep track. He plays to that one person, listening to the radio in the car or in the kitchen. His secret, he says, is being himself, or a "slightly enhanced" version, like the Berocca adverts: "You on a really good day," he jokes. "That's what I should be on air. I shouldn't be bringing bad temper. You have to bring your own genuine personality otherwise people see through it. When people hear you every day, if you're irritating them, it's the off switch."

Is he as laid back in real life? For things like today, he says, he puts on a bit of a show, "But I'm pretty easy going. It's the kind of job that if you can do it, it's not difficult."

It shows. Bruce segues as easily as he breathes; doles out the patter like a true Glaswegian. Nerves are nil, although adrenaline remains. He still gets a "whey hey, this is going well" feeling, like on days like today.

"It's lovely to be back in Glasgow and to a certain extent, it feels like I've never been away. But a complex like this," he says, gesturing to the BBC's premises, "This was all disused docks when I left Glasgow and now it's unrecognisable." So when asked if it still feels like home, he muses: "It does and it doesn't. It's now so long since I've lived here, it's not the place I left."

Home is now Oxfordshire with his third wife Kerith and their three children Murray, 12, Verity, 9, and Charlie, 6. At one point, Bruce considered moving to and commuting from the Highlands, "But now I get that rural peace without having to go up and down, because I've got a young family and I don't really want to spend a lot of time elsewhere."

Bruce became a father for the fourth, fifth and sixth time in his early 50s, after two failed marriages and three previous children: Douglas, Campbell and Kate, now grown up. The past year has also seen him become a grandfather. Becoming a father later in life was daunting, he says, but the couple wanted children; although three is the limit.

"I don't want to be standing at the school gates at 80," he smiles. "But luckily I'm reasonably fit to still carry children to bed."

Bruce's first marriage fell apart after he moved to London and met someone else, who he later married. When that marriage also ended, Bruce was shocked, experienced depression and sought therapy. He never imagined marrying a third time.

"I've been an absent father at times in the past, so this is a chance to be there and bring up a family. It's not easy," he admits. It's meant prioritising family first; being there to do the afternoon school run. But is it also an attempt to atone for the past? "Yeah," he admits. "It's just kind of saying, 'Let's do this right.'" With a messy past, he wants things to be tidy now. But life is never simple. The couple's eldest child Murray is autistic. How is he now, age 12? "He surprised us a couple of years ago. We found a way of getting him to communicate by typing. He still doesn't say much, well nothing really, but he has a terrific brain. One of the first things he wrote was 'I yearn to speak.' And we discovered he's got a sense of humour, which is fantastic."

The couple have been fortunate enough to find a teacher who believes in Murray. "It's been a real breakthrough," whispers Bruce. "He was so misunderstood for years. He knew he was intelligent, it was like being trapped. So he's sensitive about people treating him as if he is stupid; worried they might go back to thinking that. We always thought he was bright but we had no way of proving it. I hope he writes a book about his experiences one day, if we find a way of getting it out of him. He's got so much going for him."

Bruce grew up in Giffnock, the youngest of four. His father was in the shoe business and owned a newsagent's on Ingram Street while his mother was at home. He attended the private Hutchesons' Grammar and, by 15, knew he wanted to be in radio, after reading a book by radio presenter Jack de Manio. "I thought, 'That sounds like good fun,' but never thought I could do it". So he trained as an accountant before later working at a car hire firm.

But the radio idea snowballed. Despite initially being turned down for a job with the BBC, Bruce "made himself good at it" by working in hospital radio. "There was nothing else I particularly wanted to do," he recalls; and, as such, Bruce was eventually hired by the BBC and soon found himself on Radio Scotland. Although never a workaholic, Bruce reluctantly admits to being ambitious in the past. Radio 2 in London was always the goal. His big break was being asked to take over Terry Wogan's popular breakfast show in the mid-80s. It was his way in the Radio 2 door, but he knew it was "doomed to failure".

Was he ever tempted to stay in Scotland and be a big fish in a small pond? "No. I would never have been validated. I would have always wondered if I could have done it and I was damned if I was going to skulk back with my tail between my legs, so I fought to make sure I did something good."

That meant finding his mid-morning niche slot, where he continues to comfort listeners like oratory chicken soup.

Only once did Bruce consider a career change. "I never really got as far as thinking I would give it up, but I did question, 'Is this all I want to do?'" It was. "I don't have matinee idol looks or a particular talent but I've got a voice that works on radio."

Television was never a desire; in fact, Bruce resents the implication that it is some kind of promotion. Radio 2's constant evolution means Bruce has never been bored. As such, he has no plans to retire. He's got the best part of two years left on his current contract and is happy at this pace for now.

"I'll keep going as long as I'm healthy, as long as they want me to and as long as I feel it's still working.

The Ken Bruce show is on BBC Radio 2 weekdays, 9.30am.