I’ve pretty much never been one to be influenced by nefarious friends. On the whole, I’ve been fairly good at making decisions for myself, not bowing to peer pressure, even if it made me unpopular. I like to think that I’ve been consistently true to my conscience. That is, since I was about twelve. Before then, I was as malleable as blu-tack that’s been sitting on top of a radiator for days.

Picture the scene. It’s the mid eighties in Thatcher’s Britain. It’s the first month of the first year of secondary school, I’m eleven, and I’ve got a bad pageboy haircut and an ill-fitting green blazer emblazoned with a school heraldic crest that looks like a lion being sick. I’m in that starting-to-get-to-know-people phase at the beginning of a new school - forming unlikely alliances with the least offensive people in my class, the ones who look like they won’t beat me up - or at least, not straight away.

We took to hanging out before school around the local tube station, as pre-teens are wont to do, although I can’t for the life of me figure out why we were there before school, rather than after it, which would have been much more sensible. Besides, I didn’t take the tube to school - and in fact, I didn’t even live in the same direction as the tube. I lived on the other side of school, a handy twenty minute walk away. But still, for reasons I have never quite managed to grasp, I used to get up at the crack of dawn and leave the house extra early in my uniform, in order to be able to meet my new schoolfriends near East Acton tube, where we’d hang around for a bit, kicking fences and acting like disaffected youth, as we felt we were supposed to.

The loose band of us couldn’t have been further from that rebellious ideal in reality. There were five or six of us, I suppose, all vaguely well educated and well-brought up, and clearly not particularly mad or bad, because we were, after all, attending a nice strict uniform C of E school in West London. How much of a rebel can you be in an ugly blue serge skirt with stiff box-pleats? Well, precisely.

One morning, we were hooning around East Acton before school, as usual, when one of the girls in our little gang, Alison, produced a thick black marker pen.

“Go on,” she said, waving the pen in my direction, “I dare you to write some graffiti”

I hesitated. I was a good child - apart from the random penny-sweet pinching and fraudulent schemes I’d been involved with in primary school - and I’d never done any graffiti before.

Unless, of course, you count my first brush with the deep and illicit pleasures of writing in public.

When I was about three or four, we lived in a rambling manse in West London. My father’s study, an off-limits den of tempting stationery (ahh, the smell of the highlighter markers, the dazzle of the neon post-it!) was right next to the living room. One morning, my parents came downstairs to find me with pen in hand, having just finished writing a comprehensive tract on the wall of the landing between the kitchen, living room and study. Being short, as I was, the six lines of wobbly nonsense which I’d managed to scrawl were about two and a half feet off the floor, but what they lacked in visibility, they made up for in determination.

I was always fascinated with the written word, even before I could read, and I must have recognised that there was something inherently magical about squiggly symbols organised in lines and packed together like corduroy. I had set out with a thick black marker stolen from my dad’s study, and written all the letters and words and numbers I knew, in six lines, slanting slowly downwards on one side. Accuracy and neatness have always been less important than creativity.

The characters I had written ranged from the introductory but sensible “I am Meg” to the rather more strange “I like God” (well, as a Methodist minister’s daughter, you start the assimilation process young) and then a whole lot of gobbledegook. I’ve got a photo of it somewhere - I’ll try and dig it out.

My parents saw what I’d done, and instantly had an argument, while I stood there, bemused and unsure of how my work was being received. The thing is, they were torn between praise and admiration for my precocious creativity, and irritation at the fact that I’d just written in permanent ink on a wall. I can sort of see their point.

So years later, on being handed a pen by Alison on East Acton High Street, I didn’t know what to do. Should I take up the dare, write something on a wall? Or should I run away and get laughed at for the next five to seven years? The choice was clear. I took the pen.

There are two main questions to consider when contemplating a career in graffiti - what to write, and where to write it. These considerations are key in maximising the impact and longevity of your work. So, for example, something witty and creative on a tube bridge over Portobello Road is far more likely to stick around and be appreciated than a simple “I like Billy” on a school toilet wall.

The others were watching, goading me on, waiting to see if I would actually do it. I uncapped the marker and went to work.

Dear reader, if you’re ever going to be a successful criminal, don’t do what I did. Don’t leave a calling card. For reasons that I can’t recall, I opted to write in medium sized letters “Meg Pickard was here” on a cold metal pillar outside a church on East Acton High Street.

Yes, I really was that stupid.

The others were impressed at my gall and/or horrified by my abject moronity, and ran away, screeching with delight. I followed behind, blushing massively, until we got to school, panting with exhileration.

And then the guilt set in.

Oh. Oh. Oh oh. There can be no guilt in the world more burning than the guilt you achieve after doing something particularly stupid, and something which cannot be easily undone. Like posting a love letter to someone and then finding out they think you’re a moron. Or performing a karaoke turn and then realising you had your skirt tucked into your knickers. Or writing your own name on a church wall. Why hadn’t I thought to write “Julie” instead? The idiocy made my face burn with shame throughout the school day.

That night, I didn’t sleep. I became strangely, obsessively convinced that my minister dad did nightly checks of every church in West London (even the non Methodist ones), and that sooner or later he’d come across my little autograph and then come roaring home to bawl me out. I stayed awake all night waiting for his footfall on the landing.

Or worse still, God would strike me down for defacing His House. I may have liked God when I was three, as I testified on the study wall, but He certainly wouldn’t be very fond of me when He found out what I’d done to His gaff in Acton.

Unable to sleep because of guilt and shame, I got up at about six, and walked all the way to the scene of the crime in the dark. I carried with me some vim and a J-cloth, and spent a forty minutes before rush hour, before I was due to meet my friends, cleaning my name off the church pillar, scrubbing and scrubbing with harsh chemicals until my fingers were nearly as red as my face.

Only when I was sure there was no trace of my criminal act left, did I pack away the cleaning products in my school bag, leave the scene and meet my little gang of friends at the tube station, where we kicked more fences, pulled leaves off bushes and discussed playing truant for the day. But we didn’t actually do it, of course.