Image copyright Shutterstock Image caption Lorraine Kelly recently celebrated her 35th year in broadcasting

The gags begin several days before our interview with one of the UK's best-loved broadcasters actually takes place.

"Do you think you'll get the real Lorraine Kelly, or Lorraine Kelly the actress?" several friends and colleagues joke, referring to the judge who ruled as part of a tax case earlier this year that the ITV presenter had an on-air persona.

Kelly may have been one of the most familiar faces on British television for more than three decades, her warm nature consistently endearing her to viewers, but in March she successfully argued she should be classed as an entertainment personality rather than a direct employee of ITV.

The judge agreed, referring to the element of "performance" involved in making her TV show. Much hilarity followed on social media as people suggested the most cheerful broadcaster in the UK had been duping viewers for decades.

"I know people had a good old laugh about that, and that's fine!" Kelly tells BBC News. "But we all do that to a certain degree in our work. I mean, there are days that I go into work and I don't feel 100% but I'm not going to sit there and go 'poor me, poor me.'

"I've got the best job in the world, but, like every single human being on earth, you don't feel great all the time. But, you go in, and it doesn't matter what job you do, driving a bus or whatever it is, we've all got that kind of persona. You go home to your loved one and you go, 'Oh God I've had a terrible day!' But you don't do that while you're in your work, you're professional and you have to be."

On the day we meet, Kelly makes time for several fans waiting outside the BBC. She records birthday videos, takes selfies and signs autographs. You'd be hard-pushed to argue she was a miserable diva off camera.

Image copyright PA Image caption Michael Ball presenting Lorraine Kelly with her Tric Award in March

The release of her new book, Shine, comes at the end of a significant year for Kelly. To coincide with her 35th year in broadcasting and her forthcoming 60th birthday, she was awarded lifetime achievement honours at the Tric Awards in March and the TV Choice Awards in September.

Born in the Gorbals area of Glasgow in 1959, Kelly never let a working class background stop her from pursuing a career in television.

Despite an ongoing feeling of imposter syndrome ("I don't think that ever really leaves you," she says) and being told by a senior media figure early on that her accent would prevent her from succeeding as a presenter, Kelly made it to the top of the TV industry, seemingly against the odds.

But things could have gone a very different way.

'Dramatic changes'

Kelly recalls in the book the time she was replaced on GMTV while she was on maternity leave, leaving her unemployed. But a few months later, a baby food manufacturer, which was sponsoring a new mother-and-baby segment on ITV, specifically requested Kelly host it.

It was phenomenally popular, and it eventually led to Kelly being given her own daily programme. She has remained on air since, presenting the slot straight after the main ITV breakfast show. She refers to the "many regime changes" she has lived through as her programme morphed from Top of the Morning to GMTV With Lorraine, to now, simply, Lorraine.

Speaking about the significant evolution in the breakfast TV landscape, she says: "It has changed dramatically, it really has. It's no longer seen as this little cosy slot, but then I don't think it ever was to be honest because when I think about it, we tackled every single issue under the sun. More so than they would in prime time."

Image copyright Getty Images Image caption Kelly names Ellen DeGeneres and Jimmy Kimmel as two stars whose talk shows often spawn viral social media clips

She highlights the way her programme championed LGBT rights in a "pioneering way", and how it covered the Aids epidemic in the 1990s. The show has never shied away from serious health issues, and often showed demonstrations of how to spot signs of conditions such as breast cancer, encouraging viewers to check themselves.

"So I think the issues that we tackle are the same, but maybe the way that they're doing it is slightly different, particularly with Piers [Morgan]," she says, referring to the co-host of Good Morning Britain, whose combative style is very different indeed to the cuddly proposition that GMTV used to be.

"Now, I know he's a very divisive figure, but he makes me howl with laughter sometimes," Kelly says. "Sometimes I shout at him. Sometimes I completely disagree with him - on many, many things, we are polar opposites.

"But I always think people should be allowed to express their opinion. People should also be allowed to shoot them down when that opinion is ridiculous. But he is actually quite a kind person, and he's certainly taken breakfast TV by the scruff of the neck and given it a shake, and that's no bad thing."

The other key difference Kelly highlights is technology. "When I first started, there was no internet," she points out. "Nowadays, what we do is, if I've done an interview and it's 15 minutes long but we can only show five minutes on telly, then we put the big long version on YouTube." This is a strategy which has paid dividends for several US chat shows, with clips from popular personalities like Ellen DeGeneres and Jimmy Kimmel regularly going viral.

Image copyright Getty Images Image caption Kelly was pictured at the Chelsea Flower Show earlier this year

Shine could loosely be categorised as a self-help book, but it's also partially a memoir, with Kelly peppering anecdotes from her own life through her advice. She tackles issues such as good mental health and the realities of ageing, and her practical advice covers things like diet, exercise, screen time and how to keep a positive mindset.

"It's things to make you feel better inside and outside," she explains. "And inside being, I think, more important. I'm so glad we're speaking about mental health now. If you've got a broken arm everybody goes, 'Aww, what a wee shame', but if your mind is not right for whatever reason, people never used to be as sympathetic, but they are now, and that's really good."

Kelly is honest about the difficulties she's faced in her own life, including a miscarriage and going through the menopause. She feels strongly that being open and talking about such issues is crucial.

"I do think it's really important, and it's only recently we've changed our mindset," she says. "Before it was always 'soldier on, stiff upper lip', and that might work for some people, but all that does is you start getting overwhelmed.

"Five or six years ago, I suddenly felt really overwhelmed and anxious, and I'm not an anxious person. I'm somebody that just gets on with it, and I've usually got a sunny disposition, and I don't know where that went. All the life drained out of me, and I felt very flat.

Image copyright Penguin Image caption Kelly champions the positive impact exercise can have on the mind

"I wasn't sleeping, and I felt tired, but I spoke to Dr Hilary [Jones, her show's resident doctor], and he said 'it's the menopause'. And I went on HRT [hormone replacement therapy], which I know doesn't work for everyone, but for me was an absolute game changer. So I thought, if it's happened to me, it's happened to lots of people.

"And I wanted to do something on the show, but women in the public eye didn't want to talk about it. So I did, and then Carol Vorderman and Ulrika Jonsson came on and talked about it, and women like that speaking about it and being so honest really made a huge difference. With daytime telly, we can be pioneers, we can talk about things."

The book's publication precedes her 60th birthday on 30 November ("St Andrews Day - couldn't be more Scottish!" she laughs). After that, how much longer would she like to continue presenting?

"I'll do it for as long as people want to watch. And as long as I'm enjoying it, which obviously I am. Every day is different, you never know what's going to happen."

Shine by Lorraine Kelly is out now.