In this life you have to look after yourself. It’s not that your parents don’t want to take care of you; it’s not that they don’t have the best of intentions. It’s just that parents have other things on their minds. They have things to do. They look away.

Like Dad looked away from the paddling pool.

I don’t know how much of this is my own memory, and how much is what Dad told me later. Because he did tell me. He never let me forget it.

My sister Alexandra was strange and quiet from the day she was born, checking us out with her enormous dark eyes till she found she liked us enough to stay. The midwife said she was comparing the world to the way it was the last time around, and finding it slightly wanting. Mum liked this. Mum believed in reincarnation the way she believed in almost everything else, so maybe Allie really was a tsarina in a previous life. She certainly acted like one.

The first time I was admitted to her presence, I leaned on the chair arm and stared at her as Mum, Dad and a procession of friends and neighbours gurgled at the baby and ignored me altogether. Which was funny, because Allie was ignoring them entirely, too, her dark liquid eyes locked on me. If it’s possible, given that her mouth was clamped round the woman’s nipple, she was even ignoring Mum.

Not knowing what to do with my hands besides unscrewing the baby’s head or trying to pull off its toes or something (I was only three and a half), I shifted from foot to foot and thought longingly of my electronic-sound Buzz Lightyear. I already felt inferior but Nan Lola took pity on me. She was a little out of the circle too, and as I glanced up, bored almost to infanticide, I caught her mischievous smile. Her hand covered mine and squeezed it, and her creased girlish face beamed down at me and only me. Then Nan Lola winked, as if to say You’re mine now, Nick.

And I was.

Allie hardly ever cried. Not that she was one of those giggly happy babies; her silence was still and solemn and deadly calm. Apparently this is not an adorable trait in a baby, though I for one was pleased with it. I think Mum was unnerved by her ever gazing coolly into the middle distance and not looking terribly bothered.

So Allie was handed over to Dad, and they had their bottle feeds together. Very bonding, I’m sure, but it pushed me even further off the radar.

This is probably why I tried to kill her.

I remember that the day was hot, June-hot. Mum was holed up in her little understairs office in the house, on the phone to some magazine editor; Dad, of course, had gone for another beer. When Dad was sad he smelt of whisky, but that was usually in the evening. By midday he’d be only mildly gloomy, or maybe tired, and he smelt only of beer. I knew the difference very early.

That day I sat beside my little sister in the paddling pool, our bottoms cold in the freshly hosed water, our heads hot under our cotton legionnaire hats. She watched me, her pupils darker than ever in the shade of her hat brim but glittering with the sun bouncing off the pool. And I hated her as only a child can hate.

Several things riled me. Her unswerving gaze. Her silence. The fact she was only nine months old and she wasn’t even fit to play with. And the reddening of her cheekbones, the concentration in her dark creased eyes, that meant she was about to poo in her swim nappy.

It offended me beyond belief. The shameless, remorseless nerve of her. I thought about grabbing the end of the hose out of the corner of the pool, where it was still churning out water, and skooshing it straight in her impassive face. That’d make her cry, all right.

But I didn’t dare. Instead I made a face at her and shoved her hard, so hard that she toppled over backwards into the water.

I looked down at her, and she stared solemnly back. The rippling, sun-dazzled water made a sweet little round frame for her face and it was creeping up her cheeks and forehead and chin. She looked a bit astonished but not scared. I wondered whether to let her lie there and I wondered what would happen.

I knew I’d find out faster if I put my hand on her face and pushed her gently down. So that’s what I did: I pressed on her nose with a forefinger and watched.

The water was trickling into her nostrils when I changed my mind. Reaching for her wrist, I tilted her back up on to her bottom. She sneezed out water, wobbled, got her balance back and smiled at me. It was a huge direct smile, just between us. I basked in it and smiled back, loving her for the first time.

Then she was snatched up and away from me. When I squinted into the sunlight I saw Dad, unsteady and panting for breath, Allie clutched against him, and he was staring down into my face, anguish all over his own. So I knew he’d seen me from the house.

At least, he’d seen me shove her in. Then he’d come running, but he hadn’t seen me rescue her. So who did he think had pulled her upright? The pool fairies? Who would have saved her if I hadn’t been there? Honestly.

‘Never do that again,’ he shouted. ‘Never, never, never.’

You know, I think he was talking to himself.

I never did do it again. He did. It wasn’t the last time he left her, just for a minute, just to get something out of the fridge. It wasn’t that he loved Mr Carlsberg more than he loved Allie, of course he didn’t. But each time he must have balanced the possibilities, and reckoned he had a moment to spare.

So occasionally I had to stop her climbing into a filing cabinet, or sticking her finger in a socket, or grabbing a pan off the stove. Mum was very busy, writing or broadcasting, and after all she knew Dad was keeping an eye on us. Besides, I loved my alien changeling now, fiercely, violently. There’s a photo of me at five years old, the toddler Allie gripped in my arms, and I’m glaring defiance at the camera because she’s mine. My dour eyes glower out from under straight jutting brows: menacing even at that age, I was.

When Nan Lola came to live with us, Mum thought I was upset. She couldn’t have been more wrong: I was crying with sheer relief. I’d been terrified of starting school because it would mean leaving Allie to be supervised largely by Dad. Nan Lola understood this and she understood Dad, so for my sake she oversaw Allie like a benevolent hawk. She loved Allie, of course, but she guarded her principally for me. To make me happy, to make me feel secure. I was Nan Lola’s one true love and I knew that would never change.

But nobody is there for anybody all of the time. So the central fact of life is this: you have to look after yourself.