Michelle Mone: I can't always be standing there with girls in bras and knickers."

Some of you may be arching your eyebrow at this point. Michelle Mone. Private? Shy? The woman who has stripped to her undies (Ultimo, her own brand of course) for publicity pictures and then let her daughter do the same.

The woman who has managed to turn every photoshoot for her brand into a news story (hiring the likes of Mel B, Peaches Geldof, Rod Stewart's girlfriend Penny Lancaster and then replacing her with Rod's ex Rachel Hunter, much to Rod's disgust).

The woman who went through a very public divorce from her husband Michael in 2013. The woman who was a very vocal voice for the Better Together campaign during the independence referendum.

The woman who is now sitting in front of me talking about her new autobiography My Fight to the Top in which she talks about her fluctuating weight, buying sex toys with Rod and Penny in LA, the fights with her now ex-husband Michael, her sex life (or lack of it). That Michelle Mone?

It is, but, she says, not the same Michelle Mone. Everything is changing. We are sitting in the Blythswood Hotel in Glasgow. She flew up from London this morning and picked me up in a taxi from outside her Glasgow home where we were meant to meet.

It turns out the lock is broken and she can't get in. Beside her a Chanel bag. In front of her she has a glass, a straw, and a pot of hot water into which lemon juice has been squeezed.

She'd wanted to squeeze the lemon herself but after two attempts by the staff to understand exactly what she wants she has just accepted what they've brought her. "It's an LA thing," she tells me. "It clears your skin. And I've stopped drinking. Anyway. I'll get to that in a minute ..."

Her skin is indeed clear. In fact she looks great. Slim, pink-cheeked and bone china delicate, nothing like the person you see in the ultraglam, styled-to-per-feck-tion photographs.

The woman in front of me looks more natural. More, dare I say it, human. She's certainly in much better shape than when she ballooned to a size 22 on a diet of McDonalds and fizzy juice. She has taken control.

She says she's had four book offers in the last six years. "I've always felt that I didn't have enough experience to write an autobiography." What has changed? A number of things.

She was the only high-profile business person, she says, who doesn't have a book for a start. Plus, it's nearly 20 years since she started Ultimo and it is time, she says, to "close a lot of things off, a lot of speculation, because I've never spoken about my private life before".

She has now. The book. Wow, the book. It's Barbara Taylor Bradford goes Gallowgate. Rag to riches, East End of Glasgow to high-end London and LA. There are tears on every other page. It's a Hallmark mini series in waiting.

Her ex-husband Michael has already dismissed it as "a total work of fiction". He has taken particular exception to the accusation that he physically assaulted her on a flight to Miami.

But she says she has witnesses. "I wanted to make sure that he could never say 'she's making it up.' Having your lawyer there on the plane is good enough."

There have been other critics, too. The costume designer for the movie Erin Brockovich has rubbished claims that the bra made famous by the film was created by Ultimo.

Jeffrey Kurland said the cleavage-boosting underwear worn by Julia Roberts in the film was made in the US - despite Mone taking credit.

Nothing in her life seems off-limits in the book. Why so open? "I'm now speaking all around the world. I'm now number one women's speaker in the country ... I never thought that would happen ... But when I'm speaking to these people I always tell them they need to speak the truth and say it as it is. If I'm preaching that and then I do a very bland book and hiding everything I'm almost contradicting myself."

The prospect of it being read is, she admits, "very scary". Her parents told her not to do it, she says. "I always say in my life you should not regret anything and even if it has been a mistake I don't think I'll regret it. I've done it now."

Inevitably, it's her account of the collapse of her marriage that has grabbed many of the headlines. Reading the book you do wonder if she and Michael had any good times together.

They were together for more than 20 years. You wonder why it lasted so long. "Because I just thought this was normal for husband and wife to go through these difficult times. I used to be down at my mum and dad's most weekends crying and saying 'can I stay with you tonight?' And I just thought this is normal and I'm not one to ever, ever give up.

"There were happy times. But there weren't a lot of happy times. But I don't have any regrets. I have three amazing children from it and I don't wish Michael bad at all. And yes, it's unfortunate there's a lot in the book about him but it was my life. I couldn't have left it out."

Even after they separated - and while her husband was dating a designer from Ultimo - they continued to live in the same house for months, which sounds - and was - a recipe for disaster. "It was like that film War of the Roses," she admits (Michael Douglas and Kathleen Turner, if you haven't seen it.)

"When I look back now, yes, I am ashamed of myself. I couldn't help the pain and the hurt but some of the things I did were totally out of character. I've never been a bitter, jealous person. He was going to a wedding with her and he was getting all done up in his suit and I thought 'you f*****' and I put laxative tablets into his coffee."

Then there was the time she poured a bucket of water over his side of the bed and then made it all up again so he'd get in and get wet. "I am sorry for that. Sorry for that woman I became. It wasn't nice at all."

Things were further complicated by the fact that they were both in business together. Company meetings were a nightmare, she says. "It was like walking into a war zone. It was awful.

"I would never have thought when it was happening that I'd feel this way; free and happy and content and sober. And working out and my weight under control."

Ah yes, the drinking. How bad did it get? "In the book it's a bottle a night but some nights it was up to two."

Last Christmas her mum spotted a bottle of Montrechet beside her bed. "She said 'that's shocking. That's not normal. I said it's a habit. It puts me to sleep. She said 'You've got to promise me you'll give it up.'" She hasn't had a drink in 2015.

Mone's story has of course already been rehearsed in every newspaper in the land.

The Gallowgate girl who started with a paper round at the age of 10, who modelled as a teenager - Tennent's lager sacked her because she was underage - got married, had her first child Rebecca, suffered post-natal depression, became head of sales for Labatt, got paid off and then had her Eureka moment at a rugby dinner dance when she had to take off a cleavage-enhancing bra because it was so uncomfortable.

At which point she decided to design a bra. The Ultimo - complete with inbuilt "chicken fillets" for enhancement - was born and Mone became its public face.

What followed was a rollercoaster of business highs and lows. Being backed by Sir Tom Hunter. Selling six months' worth of Ultimo stock in five hours when it was launched in Selfridges.

Being conned out of six months of stock and £1.3m in the US, the banks calling in their loans and the company facing bankruptcy. The stress caused her to balloon to a size 22. "I couldn't wear my own stuff. We only went up to a size 18 and my arse was just falling out of them. I used to go to M&S for my pants."

The company was bailed out by HSBC. "That bank saved my arse," she writes. Not everyone may have the same high opinion of said bank given recent headlines.

Then there was the Lancaster-Hunter mediabomb. One of her biggest regrets, she says, is comparing the supermodel Hunter to Ronaldo and Lancaster to Falkirk FC.

Mr Stewart was not best pleased - "a devious, conniving, publicity-seeking son of a bitch", he called Mone. Gender confusion aside, his opinion couldn't be clearer. On the upside Falkirk were thrilled with the publicity.

Stewart is hardly the only person who has cast Mone as publicity seeking. There are some commentators who've always thought Ultimo received far more media attention than their bottom line deserved.

Certainly it declared substantial losses in both 2012 - when Mone and her husband may have been distracted by their ongoing marital situation - and 2013.

If I'm honest I've often wondered whether she had some compulsive need for attention. She is OCD and she admits she has an addictive personality. It can be seen in her previous attitude to food and drink after all.

Just as well she's stayed clear of drugs, I say. "I've never taken a drug in my life. I've never even smoked ... Is it a joint? I've never taken it in my life and the only reason why is, well, 1) it's illegal and 2) I'm all or nothing and if I liked it, my God. I would hate to think what would happen."

The question then is does she have a desire to be noticed too? She says not. All the attention she has sought, she says, has always been for her brand. "If we had a big fat chequebook we would have done it differently," she says.

"I was the vehicle to get PR for the business. I was the one going out and doing Celebrity Masterchef and all these different things because it would get the brand out there." All those newspaper stories have been the equivalent of a £1bn marketing spend, she says.

But there is publicity and publicity. You posed in your underwear, Michelle. Isn't that attention-seeking? "I've only done one lingerie shoot and I made a promise to Rachel Hunter.

She said you've got to promise me you'll do your own shoot when you lose the weight to inspire women and I've stuck to my word. It's a one-off and I'll go to my grave with those pictures.

They keep printing them and printing them and printing them. I'm bored of seeing them and I'm sure everyone else is bored of seeing them. And I've kind of grown up a lot since well."(It should be said there's one of those pictures in the book, but let it pass).

As for her daughter, she says she had no control over Rebecca's decision to pose. She was 21, an adult. You could say no, I suggest. "But I just think if your kids want to do something you should support them ... if it's legal. At the end of the day it wasn't my decision.

I had my partners in Sri Lanka and they were all for it. I was a bit nervous here because I knew people would say 'you're using your daughter'. Damned if you do, damned if you don't, but it was her decision.

I'm not in charge of her decisions. At the moment she doesn't want to do it again. She doesn't like the attention. She said 'Mum, I don't know how you can cope with it.'"

How does she? "I suppose you just have to say to yourself 'I've not done anything wrong'. I pay my tax, my VAT. I contribute and as long as you can go to bed knowing you haven't done any harm to anyone ... Everyone is entitled to their opinion and I don't get angry with people because they don't agree with me. I feel I've made the right decision to do it and I'll stand by it."

Anyway, she won't be appearing as much from now on. "The brand now has to start standing on its own two feet. I can't always be standing there with girls in bras and knickers."

She owns only 20 per cent of Ultimo now. Her new UTAN tanning range launches in 500 stores at the end of the month and she will continue her public speaking and there are TV opportunities she can't talk about in the offing. She's as driven as ever, but maybe not in the same way.

In the past, what made Michelle Mone run? Materialism, she admits. New toys. Pushing for the new car, the new house. She thought they might help the strains in her marriage too. "It was like Polyfilla. It smoothed over some cracks for maybe a month or so but it didn't go away."

Now she wants a change."I sat down with my mum and said there's something missing in my life. I just think there's more to me than just doing bras for the next 20 years. I want to go out and tell my story of how miserable I was.

How I fought through all the business crises. How I've turned my life around and my weight. I see people looking quite depressed and not happy about life and that's the way I was. And I'm not like that any more."

Life is changing. Rebecca has left home. Her son Declan is now working in London (they share a home when she's in the capital) and soon her youngest Bethany will be old enough to leave home too.

At 43 Mone is entering a new period in life. But she still does more than 200 flights a year. "I get bored. I've got to be running about. The last time I watched a movie was 10 years ago. I keep meaning to go and see Fifty Shades of Grey to try to get inspiration. But I'm not ready to settle down right now. Maybe when I meet someone I'll be ready to change my life, but if I'm not with my kids I don't like being on my own, so I'd rather be travelling."

Maybe the question shouldn't be what makes Michelle Mone run. It's what will make her stop?

My Fight to the Top, by Michelle Mone is published by Blink Publishing, priced £18.99.