When I was five I wrote part of a superhero story, but that was as a result of parents and family encouragement (I used to make up lots of imaginary friends and probably bored my parents and other family half to death talking about them), so I'm not going to count it as my first solo attempt to write a story. At school in English, we were encouraged to write stories all the time, usually with a prompt from the teacher. One parents' evening comment from one teacher was that no matter what writing prompt she gave, I'd manage to set the story in ancient Rome. (I was fascinated (aka obsessed) with Roman history when I was 7-8.) I also made up loads of stories at home, all the time, relentlessly, mostly acted out by Lego people or other toys.

My first 100% solo attempt to write a story was when I was 12, because I used to love writing stories at school but the teacher didn't set enough pieces of work that involved story writing. Instead it was boring stuff like writing book reports and business letters and stuff. Then I had a revelation - I could write at home. On my own. Whatever I wanted. It was an amazing revelation and I haven't stopped writing since then.

My first stories when I was 12: one was a story about space pirates inspired by the 1980s computer game Elite. Another was about a boy called Jason whose dad beat him and he was taken into care. The only one of my early stories that I've actually kept is a novel length story I started writing age 13 about a boy whose older brother was a sort of mini Godfather of all the crime in the local area. It would've been an 18 certificate if it'd been made into a film*, full of drugs, violence, prostitution, abuse/manipulation, drug smuggling, guns, suicide, and "dark themes" (as the BBFC would put it). This is no reflection of my childhood though, which was pretty ordinary. I blame Shakespeare. I was trying to out-do him for number of suicides and the dead body count by the end of the story.

*not that it would've been, because the quality of the actual writing was dire. My earliest novel-length stories were written in one single, huge paragraph with no regard for the rules of things like punctuation and spelling. I could read them, that's all that mattered.