Usually when I run writing workshops they're for children, students and teachers. It’s always fun and satisfying because I’ve done it often enough now that I know they’re going to enjoy the material I’ve got for them, I know they are going to write well. But last year I did two workshops in prisons and while I hoped they would be as useful for the prisoners, I went in with entirely selfish reasons. I’ve never been near a prison before and I wanted to see inside that world.

But usually the people on writing workshops have chosen to come and they already have ideas they were working on. This time I was going in with Geese Theatre and we were working toward the Clink and Arts Alliance project Write to Be Heard. It's a National Prison Radio project with the aim of getting prisoners to write and specifically to write for radio. I'm a radio man, you don't have to sell me on writing for radio but there was an extra element here in that writing to be heard is different from writing to be printed. Prisoners who struggled with grammar or English – everything was to be in English and anyway my own three languages are English, American and Australian – would hopefully feel less pressured to get the commas right.

I was scared. I’ll admit that freely: I need my commas. And prisons. All those big, imposing walls. You see so many prison dramas and I’ve even written one: my very first Doctor Who radio drama had Peter Davison locked up in solitary in an alien prison. The high security, the heavy doors: it’s an imposing and a frightening world.

It's also a world. You're not stepping into a community per se, it is a world entire of itself. The air is different. You're much more conscious of the open sky above you because of the closed walls on all sides. You never find out what any person did to get locked up but you know every person did something. And you haven't. They are all at a different place from you and you want to understand it, but you vividly don't want to experience it.

Plus, it's a criminal offense to bring a mobile phone into a prison so my iPhone security blanket had to stay outside in the car.

Once you're through all the walls and the doors and the dogs and the guards and the forms and the photographing, though, you're working in a room that could be anywhere. I did two prisons in two days, back to back, and the first one was like working in my old sixth form. Apart from the prison guard watching all the time, there were low-slung seats, school-quality tables, plenty of room. It was a low-security prison where everyone I met was in the last stages of their sentences so they were very much looking to the outside world.

It meant I got writing from them that was one moment introspective, the next quite liberated. One moment unexpectedly happy and one moment very piercingly dark and personal.

The second group was in a higher-security prison. Even more serious walls and, this time, retina scans. The group I got was made up of primarily young offenders who were in on drug-related crimes. Some had been there a long time and none of them leaving soon so you knew there would be a bit of a different mood.

Unfortunately, there was also a mistake. For whatever reason, these men hadn't heard of the project, they didn't actually know they were going to be doing any writing. They came along expecting to watch some kind of performance.

Okay. So I have fifteen men, some deeply troubled, all scary, none wanting to be in prison of course but also none choosing to be there because they wanted to write.

Whatever you're picturing now, add in that we were today in a pair of portacabins bolted together. With myself, these men, Geese Theatre people and prison staff, we all had to take turns breathing in and out.

But also picture this. In moments, I had that room in silence.

Everybody writing. Really concentrating, very serious.

And then I had them all performing their work. Everybody talking, really concentrating, really laughing.

I write to be read. I forget that writing can do such big things as focus us and release us, that it can take us away from ourselves and push us deep into ourselves too.

Plus, very many of the men I met went on to enter the Write to Be Heard project. I can't be more specific: I can't tell you names, what prisons they were, I can't really tell you how well they did in the project. But in a counted-them-out-and-counted-them-back kind of way, let me tell you that when I heard the results, I was proud of them.

I've been wanting to tell you that and in fact about all of this for six months or more but it's only now that I'm allowed to talk about it publicly. Which is good because I get to tell you but it's great because there many of us writers did very many days in a huge number of prisons and I'm hoping to hear from everybody else now too.

Thanks to Clinks.org and Arts Alliance for having me and to all at Geese Theatre who I'd heard of but truly did not appreciate how much they do in prisons and for prisoners. And to Writing West Midlands whose Room 204 project got me the gig.