"What does that even mean?" asks Miriam O’Callaghan when I pitch her the old chestnut about having it all. From the outside, the 59-year-old RTÉ journalist (the definition she prefers) does seem to fit that bill.

One of the highest profile figures in the country, mother of eight children, happily married to Steve Carson, recently described as the "boss of things at BBC Scotland", ambassador for numerous charities and causes and even linked with the highest office in the land  a couple of years back (of which more later).

Yet the question hangs, posing that other unanswerable query about happiness. "Life is not about perfection for me," she says. "It’s about trying to fit everything in but always focusing on the children first because ultimately, that’s what matters."

It’s Tuesday morning in RTÉ. O’Callaghan, direct from a Prime Time meeting, is sporting a denim jacket over a bright summer dress. Last time we met it was a leather biker jacket. Even if she says she’s boring and conservative, the broadcaster’s style has always had an unexpected kink (she still plaits her hair occasionally, hippy-style), as if she gives a damn.

As ever, she’s as bubbly as a flute of champagne. And as ever, she’s careful with her answers (certain subjects like gender quotas cannot be discussed because of her role as a current affairs anchor). If there’s a vulnerability or frailty, Miriam hides it well. "I’m made of sturdy Kerry stuff," she says at one point, a nod to her lineage (her late father, Jerry was from Currow), someone who won’t be forced off social media by the trolls or is likely to moan about her lot.

"My motto has always been ‘Get out there and do it’ and when I now go to talk to young girls in schools, the line is that ‘If you can’t see it, you can’t be it’. So, the best thing I could do, as a working mother, was just to get out and do it."

Yet it was, and in many ways still is, a man’s world. "When I started having my children in my mid-20s, it was very, very difficult because you daren’t bring up the fact that you had kids or that a child was sick. So my philosophy has always been to accept that it’s an unfair world and do your best to overcome that by fighting your corner.

"I know that women have fought for generations to get the right to take maternity leave and you should. But for someone like me or those who are self-employed, it’s more difficult. If I had taken full maternity leave for each of my eight children I wouldn’t be doing what I’m doing now and that is the harsh reality of life."

O’Callaghan is wary of being put on a pedestal as an ideal of working motherhood to aspire to. "But I’m imperfect and along the way I’ve messed up so much in trying to balance life and work," she says.

"Something gives at the end of the day. If you are going to have a large family, you have to be there all the time for your children. I never missed a parent-teacher meeting, I never missed a school concert but at the other end, I remember running into Prime Time at 9.28 and my editor wondering where I was. But I knew that those parent-teacher meetings were never coming back and I erred on the side of never missing them and flying by the seat of my pants at work."

Life is unfair – a mantra that fires her and drives her – comes from her ‘annus horribilis’, 1995. That year, her sister, Anne died, six months after being diagnosed with cancer; eight weeks later her father had a stroke and also died; and Miriam’s first marriage, to the broadcaster, Tom McGurk, ended. "Before that, I was pretty blessed," she says.

"Now the older I get the more I believe that there is a lot of random good luck in this world. Sure, you can make your own luck but sometimes life just comes and throws massive harshness at you and you either go on or you don’t. Now I wake up relentlessly happy every morning, but I’m just incredibly grateful for my life. That’s not an act. Anyone who lives with me will say I am nauseatingly positive."

Of course, life can be sweet too. "When I first met Steve in 1995, Anne had just died. On a drive to Achill Island, where we were making a documentary on the Famine, Steve told me how his mum, Patricia, had died when he was just four years old. He hadn’t really talked about the death of his mother much before then, but I was fascinated.

"I wanted to know if my little nieces, who were two and four, were going to be fine. I said to him then how sad it must be for him and his father and his siblings but more than anything how it must be for his mother because she was robbed of her life, as my sister Anne was. Steve and I fell in love but that loss we both suffered remains a real bond."

Last March, O’Callaghan claimed that she had been defamed in a series of "false" and "malicious" adverts containing her image on Facebook and Instagram. The adverts, which were linked to offers for skincare products, suggested wrongly that the broadcaster had left her job with RTÉ’s Prime Time. But if you expected it to make O’Callaghan more wary of social media, you’d be wrong.

"I love social media," she says. "I have an ongoing court case with Facebook and can’t talk about that but I’m still on Twitter and I use Instagram. I find Twitter invaluable for my work as a journalist and I find that it has got less nasty.

"In the past, I was trolled but now people are more polite. Maybe that’s because there have been court cases taken against people in the UK who were nasty online. But I find it fascinating medium and I wasn’t going to let the trolls drive me off Twitter. As I told you, I’m tough."

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Such toughness probably owes something to her mother, also Miriam, still going strong in her 92nd year: still driving her own car, still ringing Miriam to talk politics ("She knows more about current affairs than me"). In the past, O’Callaghan has described her DNA as very conservative, the daughter of a school principal and a senior civil servant, but she still sees herself as a risk-taker.

"I had the most conservative upbringing and went to UCD at 16. I was very shy in college and I’m still quite quiet. I got more confident in my own skin as I got older. Some say that post-40 women become invisible but I’ve never believed that. Nobody looks at George Clooney and says he’s past it."

But he’s a man, Miriam! "Well, that’s true but things are changing for women in a Hollywood that was run by men."

Earlier this year, Miriam underwent surgery to correct a misalignment in her eye. "I had developed a ‘lazy eye’," she says. "Apparently you are born with it but my mother denies any knowledge of my lazy eye", she laughs. "But it was annoying me and I noticed it myself, especially when I was reading the autocue.

"I went to Professor Michael O’Keeffe in the Mater but not everyone would be able to do it. It involves cutting the muscles in both eyes when you’re under a general anesthetic and when you wake up they adjust the stitch in one eye. Most people might think ‘AAARRRGH!’ but I was absolutely fine with it. I was in the hands of a brilliant eye surgeon and I’m delighted with the results."

It will be the second summer without her seasonal TV chat show. Miriam doesn’t miss it. "Honestly," she says. "I will be doing six weeks of radio [covering for Sean O’Rourke] from Monday to Friday. Not having to do a Saturday night show is so liberating, especially as my children felt that I was never off."

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In any case. she will have Sunday with Miriam, a breezy radio chat show where she finally nailed her wish-list guest, Van Morrison, last December. But she is just as buzzed interviewing ordinary people with extraordinary stories, people like Vicky Phelan and Ruth Morrissey. And she lists the late Seamus Heaney as one of favourites of all time, a man who gave her that line about treating everyone, even the nasty ones, with "implacable courtesy".

Is she an impulsive person? She shakes her head. "Impulsive?" she repeats querulously, as if wondering what it actually means or whether it might explode in her face. "I suppose the last time was a few years back when I went to Las Vegas with my daughters and a few friends for a few days.

"Steve came home saying that he would be going on his annual rugby match outing with his old school friends and I told him that I’d be going to Las Vegas that Friday. He said ‘WHAT?!’ and then laughed. But in truth, I’m quite boring. When you have a large family they just want you there in the evening. I’m a creature of habit. I get the same takeaway and I like to visit the same places." 

Yet last year the word was that Miriam O’Callaghan was considering running for the office of President of Ireland. "I used Twitter to put out my own statement that I wasn’t running when things got really wild," she says of her decision to knock all speculation on the head in April 2018. So is that story finally dead and buried? "All I can say is that I don’t plan ahead. I love what I’m doing but never say never to anything."

Even as she dangles a possible future, O’Callaghan goes back to basics. "First and foremost, I'm a journalist," she says, citing a recent Prime Time documentary, Carers in Crisis, which has been nominated for the Celtic Media Festival. "People are endlessly fascinating. I love chatting to people and it’s not something I feign for the cameras."

And it is nice to chat with Miriam: empathetic, fun, ambitious and tough. "You can ask me anything," she says but that's no guarantee you'll get the answer you want. And when you think you're close to the real Miriam you're probably farther away than ever. Or maybe she's simply what she says she is: relentlessly optimistic, nauseatingly positive.

The sum of her upbringing and a life lived at full throttle even if you suspect the wrestle between Conservative Miriam and Risk-taker Miriam is ongoing. "The one good thing about me is that I’m constant," she says. "What I believed in 20 years ago, I still believe in now. But when people talk about having it all I don’t understand that. You can’t have it all. You can only live the best life you can for you and those around you."