Everyone plays superheroes, don’t they? When I was at Wootton Primary, every time the bell rang for playtime, we bolted outside to don our invisible costumes and defeat evil villains. But when you’re playing a game with a mixed-gender group, the options for the female roles needed to be bigger than one.

As a young person, I was also introduced to Superman, Luke Skywalker, James Bond. They were cool too, but it’s quite hard to imagine yourself as a macho, testosterone-fuelled, weapon-wielding hero when you’re a girl. And yet I did want those adventures. I wanted to be the one saving the universe. And so I wrote stories about girls doing cool things and meeting mystical creatures and saving their handsome-but-helpless heroes. I was lucky to have a fantastic English teacher at my secondary school, Our Lady’s Abingdon, who gave me a love of Shakespeare and Milton – and also came up with great creative projects. Thanks, Miss Hemingway!

At the age of thirteen, I saw the film Labyrinth – and there was my heroine. Jennifer Connelly did it all – met the fairies, saved the world (all right, her baby brother) and defeated the Goblin King – AND wore a huge ballgown. Right at that moment I decided my future career – but it wasn’t writing. The only way I could live in a fantasy world like that was to be an actor, so that’s what I did. I studied Performing Arts at Middlesex University and spent five years touring the country in all kinds of plays and musicals.

But I still wasn’t Jennifer Connelly (unsurprisingly). I still wasn’t saving the world – so I started writing stories again, alongside a new job as an English teacher at Wychwood School in Oxford. I loved teaching: the possibilities it gave for interesting discussion and creative work; the fascinating insight into teenage minds. The stories I wrote then were contemporary: teenage girls facing issues such as divorce, depression, self-harm, whilst determined to find their way in the world and make their mark. None of them based on any of my pupils, I hasten to add. But the people we meet do inspire and spark ideas – I think any writer would agree with that.

It’s taken me 12 years and 24 published books to do it, but I have finally created a female superhero – a proper one. Holly Sparkes is standing on a hillside one day when a ball of lightning comes shooting over the sea and strikes the mobile phone mast behind her – sending an arc of electricity straight into Holly’s chest. When she wakes up, she discovers she can create and manipulate electricity. But should she use it to bring down the school bully, to switch on the TV from the other side of the room, or to defeat an evil technological genius, hell-bent on destroying the internet? Why not all three?

ELECTRIGIRL was published by Oxford University Press in February, and the second in the series, ELECTRIGIRL AND THE DEADLY SWARM, has just followed suit. A third is due in May 2017. It is enormous fun to write, and has the added excitement of being told partly through comic strips, drawn by the talented author and illustrator Cathy Brett. The first book was The Times’ Children’s Book of the Week, and I’ve since met and heard from many children – girls and boys – who have read and loved it. Librarians love Electrigirl too because it encourages the more reluctant readers – and they recognise the importance of giving girls powerful heroic figures to read about. When I visit schools, I am often asked, ‘Is there going to be a film of Electrigirl?’ One day, I hope. The world needs more female superheroes, and I’m having way too much fun to stop yet.