Mandasue Heller is a 47-year-old, softly spoken, rather shy, slightly insecure grandmother who spends her nights singing and her days writing about crime, prostitution and drug-dealing in Manchester council estates. It’s the insecurity I don’t quite get.

After all, if you had published nine books in seven years and sold no less than a million copies you’d feel entitled to be a little full of yourself, wouldn’t you? You might at the very least think you know what you’re doing. Not Heller. “Every one I hand in I think, ‘Oh, this is the one the editor’s going to think is crap.’ I’m more nervous each time.”

We are sitting in the bar of the Malmaison hotel in her home town. That’s me, Heller and her partner Win (short for Wingrove). She’s brought him along for support.

They met 14 years ago. “Win’s a musician. I’m a singer and I’d been in a band that had split and I was looking for something else. Win was looking for a singer so we met like that but we didn’t get together immediately. We just worked together. Then I got a tumour in my eye and had to stop singing.”

Heller does this a lot, just chucks something out of the blue into the conversation, another casual detail from her life; like the time as a kid she was headbutted by an adult. Or the time she worked on a Tarot phone line. Or the time her son was told he didn’t have to turn out his pockets because the gang that had stopped him recognised that they had jacked him the day before. She’s full of stories and her own are nearly as rich as the ones she writes.

It’s possible you don’t recognise her name. It’s true she doesn’t tend to get written about in the quality papers. But then, as she says, she’s not writing literary books. “I’m writing about crime; nasty, gritty. I’m not trying to make anything gory or really nasty, but people are capable of very nasty things.”

Indeed they are. In her new book Two-Faced, the main thrust of the story is about a pair of identical twins. One wants to become a model, the other a social worker. Unfortunately they get themselves involved with the criminal underworld and in particular a rather deranged gangster with control issues and a sideline in sex trafficking. Imagine a wild distillation of soap opera plots, gossip magazine headlines and Crimewatch reconstructions, told plainly but grippingly. They’re fun if at times gruesome. She’s often been called the Mancunian Martina Cole, the bestselling author of 14 novels set in London’s gangland, and the two writers do share a publisher.

“I’d never heard of Martina when I started,” Heller says. “We’ve met since. We’re good friends and neither of us thinks we write the same.”

But we haven’t finished the story about the tumour yet, have we? This was back in the 1990s, when Heller was pouring her energies into being a singer.

“I saw a neurosurgeon a year before it was diagnosed because I was having really weird symptoms and he told me it was stress-related migraines. So I went away feeling like a hypochondriac. But when I was driving I thought cars were driving at me when they were actually driving past me because my vision had gone so weird.

“Then, when I woke up one morning it felt like my eye was literally dropping out. I had to hold it when I sat up. So I just went straight to the eye hospital and said, ‘please look at me.’

“It was on my optic nerve but it bent it the wrong way, which is why I was seeing weird things. It was as big as my eyeball and it was literally pushing it out. I was told three more months and I would have been dead because it would have broken through my skull. So that was pretty fortuitous.”

Well, just a bit. She met Win again shortly after her operation and they got together. He didn’t even notice the scar around her eye. Until then she’d always seen singing as her escape route from the dead-end jobs she’d worked in. But recovering from the operation she was forced to stop singing, so she started writing instead and there were things she wanted to write about.

Mandasue Heller grew up in Warrington, in a “really rough area” but in a house that was showbiz central in the north west of England. Her parents knew the likes of jazz stars Acker Bilk and Kenny Ball and they’d invite them to stay when they were touring in the area. “They’d have these mad showbiz parties that me and my sister were too young for and we’d be sent to bed.” She says her mum Jean looked like Elizabeth Taylor – “gorgeous, stunningly gorgeous” – her dad, Ian, a bit like Jimmy Cagney. They split when Heller was nine. “A bit acrimonious. We went off with mum.” She lost touch with her dad for many years. They got back in touch, “but it’s one of those relationships that didn’t really hold”.

She’s still “ridiculously close” to her mum and her sister Avajane. Jean was a teacher and involved in am-dram. She even did TV work as an extra. Heller would do the same later herself, though she always found it boring.

Heller moved to Manchester in 1982 when she was in her early 20s. She moved with her sister into Hulme Crescents, a set of high-rises built in the 1960s.

The Crescents had been built to house people who had been decamped from the terraced housing which was being pulled down across Manchester, but families never took to the cheaply made high rises and so by the early 1980s they were occupied by musicians, students, artists and poets.

For a while Heller loved it. “It was just like Glastonbury all year round. It was fantastic. I was in a rock band and there were numerous other bands. Mick Hucknall started off there, [his first band] Frantic Elevators were in there. We all used to play on the grass outside, get all the equipment out, doors open. It was just constant music.”

And then the drugs came. Heroin killed the good times. The Crescents became junkie central. Heller’s sister went off to Stonehenge in a van with her boyfriend and a baby and Heller ended up on her own “surrounded by heroin addicts”. Everyone she knew got into it. Even her own boyfriend. “I saw a lot of death, a lot of life destruction. It never tempted me because of that.”

Her boyfriend’s addiction destroyed the relationship. “I had a baby and I just couldn’t deal with it because the baby had to be the priority. So I’d rung his mum and dad and said: ‘Come and take him away, please take him home. He wouldn’t stop for me so they took him away, left me with the baby.”

And that’s when things got really bad.

There is a scar down the back of Heller’s head, a few inches long. It is hard to see, but it makes her hair grow in a funny shape, she says. The scar is a marker of what she’s been through. It’s also a symbol of why she started writing in the first place.

The story goes like this. She was living in a maisonette on the estate. Her sister and her boyfriend were back visiting from Stonehenge. Heller, who had let them have the bedroom while she slept on the couch with her 10-week-old son Andrew, heard footsteps on the stairs.

“I woke up with a start and the door opened opposite me and I saw this man in silhouette. He just ran and jumped on top of us. Andrew started screaming. We were on a couch that slotted together, so that separated and we all landed on the floor. All I could think about was, ‘He’s going to kneel on the baby’s head and kill him.’ I remember shouting, ‘The baby, the baby,’ and the next thing he was gone.

“Andrew had gone quiet so I grabbed him and shook him, thinking he was dead, and he started crying. My sister and her boyfriend obviously woke up and came running in. They thought I’d been dreaming because there was nobody there.”

But then they found a glove under the quilt on the floor. “It was obvious somebody had been there and when Ava’s boyfriend went down he found the door lock had been ripped out. “Then I put my hand through my hair and it got covered in blood. I had a huge gash down the back of my head. He’d hit me with a claw hammer. I hadn’t felt it.”

If anything, she says, what followed was worse than the attack itself. The police assumed her boyfriend had attacked her. “Then they were looking around and Ava and her boyfriend had brought a video player so the police said, ‘What does she do for a living? That’s a nice video recorder.’ The implication was that I was a prostitute and the guy was my pimp or one of my punters.” The police even made her walk from the hospital to the police station “with all my hair shaved off, blood all over me, big scar, stitches” to give a statement. “It did sour my opinion of the police for quite a long time.”

The emotional aftershocks stayed with her too. She couldn’t sleep unless she was surrounded by people and she was obsessed with the idea of protecting Andrew. “If I was in the house by myself I had a hammer under my pillow. I had knives. I had all sorts. I went really peculiar.”

It was some years before she thought of writing about what had happened to her. Years and that tumour. She’d always loved reading, borrowing her mum’s Sidney Sheldon books, though her favourite was Xaviera Hollander’s The Happy Hooker. She was going to call her daughter Xaviera but everybody told her that she wouldn’t be able to spell it. “So I called her Azzura instead.”

She’d liked writing poetry and when she started singing she would turn her poems into song lyrics. But then the tumour stopped her singing and she started to write. “While I was laid up I thought ‘I have to get rid of this attack. I’ll write about it’.”

What she wrote was too personal, too painful to publish, but it did exorcise a lot of the demons. And she found she liked writing. So she started making stories up. Her mum phoned her one night to tell her there was a programme about wannabe writers on the telly. She watched it horrified, seeing all the rejection slips that seemed to be par for the course. But one of the six writers, Jake Arnott, did get published. “I thought, he writes crime and I’m writing crime, let’s see who he got published by.”

She sent off her manuscript to Arnott’s publisher and it was picked off the slush pile. The Front was published in 2002 and there’s been at least one book a year ever since.

Now and again she’ll draw on past experiences for inspiration. She says she’s sure there’s a book in tarot lines, something in the meeting of despair and dubious ethics. “People who ring those lines are desperate to get an answer for something. I think it’s just outrageously unfair the prices they’re being charged and they’re being told a load of rubbish.”

When she was working the phones she tried to be empathetic. But it’s not easy when you’re under pressure to keep people on the line as long as possible. Also, while you’re talking you can hear all the sex line workers who were in the same office. “The women who were working those sex lines were old. I got a lift into work one morning and there was an old lady with her leggings and her big jumper with the reindeer on waiting to go in and she was about 70-something. And I said to my friend, ‘See her, she’s blonde and she’s 20.’”

Has success changed her? She doesn’t know. “I think age has mellowed me,” she allows. “As a teenager I was very volatile and then I went through all my insecurities.”

But life is good now. Her two sons Michael and Andrew are grown up and off working in China and Australia. Azzura is due to give birth to her third child any day now (a boy duly arrives the day after we speak). Heller is close to her mum, sister, kids and Win’s two kids. She’s back to singing. If she has an ambition it’s that one day she’d love to sing with Lisa Stansfield.

With Win she has formed a band now playing guitar rock. They’re called Dakota, although that might change. They’re starting a soul covers band too. Her favourite cover songs to sing, she says, are Reach Out I’ll Be There and Never Can Say Goodbye. When she sings them, she says, looking over at Win, “I’m thinking of you.”

She says she feels “incredibly safe with Win”. Her past is in the past. Well almost. “I can’t be by myself in the house still. Because if I hear a noise I’ve got a weapon.”

Mandasue Heller knows the world she writes about. She’s got the scars to prove it. If you get close enough, one of them is even visible.

Two-Faced by Mandasue Heller is published by Hodder & Stoughton, priced £11.99