When I was five years old, my dad decided he was bored with family life and he ran off with another woman. He didn't bother leaving Mum and me any details about where he was going or how we might contact him in the future. And he certainly didn't leave any dosh. My mum cried continually for months and then she started drinking. A lot.

From the age of five to nine, I looked after her. I got her out of bed, I cleaned the house (not very well) and I got us food. We ate a lot of bread and jam, seeing as I wasn't that great at cooking when I was five. Or rather I ate it and my mum either toyed with it or fell face-down in it. That bit of my life seemed to go on for ages, but it was probably because I was so young that it felt that way.

When I was nine, I came home from school one day (early as usual, having sneaked out of my class while pretending to go to the toilet because I was worried about mum, who'd already been drinking that morning when I left for school) to find a very glamorous, older woman sitting on the sofa.

Our flat – on a council estate, not a pretty one – looked a lot cleaner than usual. I could see that the carpet had been vacuumed, the shelves dusted and the plates, empty tins and over-flowing ashtrays had been cleared away. The woman sitting on the sofa was wearing a deep blue velvet dress that sparkled as she crossed and uncrossed her legs because of silver threading that ran through it. She had blonde, silvery hair that touched her shoulders and she wore a lot of make-up. I especially liked the dark plum nail varnish and the deep red lipstick. As she spoke she waved those beautiful hands (she had heavy silver rings on at least three fingers) around in the air.

My mum sat across from her in the armchair. I could tell she had been drinking, but she wasn't quite as drunk as usual. I couldn't tell what mood she was in – good, bad, unhappy, pleased to see this woman, not pleased. Who knew? She was smoking though, and her hand shook a little as she dropped the ash into the ashtray beside her. It made a nice change for her not to be using a kitchen plate, I thought to my nine-year-old self. At least I won't have to wash that up afterwards.

The woman swung round to face me. "Hello pumpkin! I was just talking to your mum. Do sit down."

I sat; and I didn't say anything.

"Angela, there's no doubt that my son is an absolute –" The glamorous woman said a very rude word that I won't bother to repeat here. It did sound cool coming from someone who spoke so posh.

"...what I suggest is that I pay for you to go into rehab and I'll take the munchkin here for a while, now that I'm back in this country. How does that suit, darling?"

It took me a few moments to realise what she meant. Mum was going away for a while and I was going to live with a stranger for a few weeks. For a few minutes, I thought about crying, or even trying to say no. But then I remembered what my everyday life was like.

KATIE'S LIFE – AGED NINE

7am: Wake up and go through to mum's room to see if she is awake/conscious.

7.05am: Some mornings she was awake: good. Most mornings it takes me five minutes to shake her awake: bad.

7.10am: I make us bread and jam or bread and cheese spread. They talked to us a bit about healthy eating at school recently so from time to time I make us fresh fruit.

7.25am: I wash up. I persuade Mum to go for a shower.

7.45am: I have a shower, iron some clothes (not very well) and get dressed.

8.15am: I leave to go for school. As I shut the door, I can usually hear Mum clinking glasses or bottles.

9am: I sit at school worrying about Mum and try to sneak off either at lunchtime or early afternoon.

2-3pm: I get home and find Mum drunk. I clear up the mess, get her into bed and then I tidy up. After that I watch telly. I watch anything I want, seeing as my mum can't tell me not to. Sometimes I go out and leave her – I go to my friend's house, but she never comes here because I won't let her – but a lot of the time I'm too worried about my mum to leave.

6pm: I wake Mum up. She talks to me for a while. I can tell she feels bad about what she does to me, but she can't help herself. Sometimes she makes us stuff to eat, which is great because she is a good cook and she likes to make me lots of chocolate puddings. Other times, she gets a bit upset and cries as she talks to me. I hate that.

8pm: Mum starts drinking again. I go to bed about 10pm.

So, it was an easy decision really. I agreed to go with the glamorous woman. She said she was my gran (my father's mum) and that she had been in America for the past 10 years. She didn't explain why she'd never come to see us before or why I'd never heard of her. Oh well, I don't think my nine-year-old self cared.

Gran took me to where she lived, a very smart town house. It was nice for me to find myself suddenly living in such a big house and to have so much space. The house was in a new housing development, an area of the city I'd never been in before. Gran said she hated old houses because they were so draughty and she couldn't bear the cold, having lived in a warm country for years.

I think most people expect grans and other old people to live in ancient houses, with banisters, stuffed animal heads on the wall and funny looking paintings of the countryside or people from 200 years ago with weird white wigs on their heads. I saw a TV programme once about an old lady who lived in a stately home, so that's what made me think old, rich people lived in houses like that. (I could tell Gran was rich; she wore lots of jewels, drove a big car and she spoke dead posh.)

Gran's house had wooden floors and sheepskin rugs everywhere. She had three bathrooms so we had one each and one spare for 'best'. In her kitchen, she had a dining table and she made us eat almost every meal there.

"Pudding – and you are my tubby little pudding, aren't you poppet? – it is the last bastion of civilisation to dine at the table and not in front of a television or computer." She had some funny ideas Gran, but she was very strict about some of her rules and I gave up arguing after a while.

It also made a nice change not to do any housework any more, as a nice foreign lady came in to do it. Gran did all the cooking so we didn't eat jam sandwiches or chocolate cakes any more. (I missed the chocolate cakes a bit, though.)

Best of all about living with Gran though, was not having to worry about coming home to find my mum drunk. My mum came out of rehab that first time after a few months. I thought she looked better, her skin was not grey any more, her eyes looked brighter and her face didn't look so pinched.

I asked her what rehab was like because I had no idea what it would be like. She stared off into the distance and then screwed her eyes up.

"It was OK, I found out a lot. But I had to share a room with another woman and that wasn't so good. I felt as if this woman was watching me all the time – maybe checking to see if I had any booze on me so she could nick it. And we all had to talk a lot about ourselves."

She promised me that first time she was reformed, she would never touch a drop of "the demon drink again", that she would be a better mother and I could come and live with her once she'd found a job/nice place to live, blah blah. She was back drinking again a few weeks later.

Over the next few years, this happened six or seven times. Mum started drinking again, she would stop, she would promise to be a better mother and never drink...Gran and me decided it would be best if I stayed with her permanently. When Mum was out of rehab, I visited her. Sometimes we had a laugh together, but most of the time I was relieved that I lived with Gran. My life was completely different.

The biggest changes though, came when I started Ballingham High at age 11. Gran had home schooled me when I first moved in with her. It was much better than going to school. For a start, sometimes we took days off during the week and sometimes we started after lunch. On sunny days, we went for walks round the local parks and I had to tell Gran what all the trees and plants were. On rainy days, we often went to museums or we visited old houses and made up stories about the people who used to live there.

I had wanted this life to continue – Gran had made everything such fun. But, she said, she couldn't teach me maths as the subject bored her and she felt I probably needed to learn some other subjects too.

She also said teaching me was taking up too much of her valuable time. I disagreed. I could add OK (I used to add up how much my mum was drinking, for example) and I was hurt that she didn't want to teach me anymore, but she said as I was only 11 my opinions "weren't as important as hers" so big school it was.

Ballingham High was the nearest school to Gran's house and Gran said she wanted me to be able to walk to school (maybe I might lose some weight that way she said, COW!) so that's why I had to go there.

I was a bit surprised she had chosen Ballingham High to be honest. We'd walked past the school a lot in the time I'd been living with gran. Everything seemed so noisy – screams, music playing, laughter and the odd person crying – and I always stared at the girls who went in and out of the school gates. They looked pretty and confident, in their customised red and black uniforms. The blazers would have the arms cut off and most of them were wearing very short skirts and those tights that look like stockings and suspenders.

They wore their hair long and straight, they were a peculiar orange colour (Gran said it was "vulgar fake tan") and they shouted across the playground to each other as they sauntered out of the school gates, pushing past me as if they hadn't seen me standing there. They terrified the crap out of me.

I dreaded going there, but Gran wouldn't hear of anything else. "Munchkin, you're going there and that's that."