Actor turned playwright, David Parnell, whose new play Taste opens tonight in Dublin, on how one day he realised he'd become a writer.

The old joke has it that two actors are sitting having a pint. Neither are working. One says to the other, "I'm writing a play". And the other replies, "yeah, neither am I."

It's Alison McKenna (of Bespoke theatre company) that I blame. There I was, happily minding my own business, scraping a living as a jobbing actor, when along she comes and says, "if you write a play, I'll produce it." All right, so it wasn't quite as simple as that. We'd been friends for years (had started Baois theatre company together), and every opportunity I got, I told her, "I'd love to write a play". But what gave her the idea that I could actually do it is anyone's guess.

Maybe it was the one-acts. Alright, I admit, the two one-act plays that I wrote while still a student probably had something to do with it - they may have given her the notion that I might be daft enough to attempt to write a full-length play someday. But, really, what kind of evidence is that to base a thesis on? He writes two one-act plays in college, he constantly talks about writing a "proper" play, ergo, he's a playwright. Nice one, Alison.

But, she persuaded me. That first play was Licking the Marmalade Spoon, and, true to her word, she produced it. It was one of the last plays to be performed in the old Project, before it was Temple-Barred. And I will always be grateful to her for that. Because, in the same way that my once passing through New York for a day allows me to say "I've been to New York", so sitting down to write that first "proper" play allows me to say, "I wrote a play." Even if I never manage it again, at least I've done it the once.

I have acted a lot, on most of Ireland's stages - the Abbey in particular. In fact, I'll be acting there again in the new year. People sometimes tell me they would never have the nerve to walk out onto a stage in front of all those people. Well, to me, that's a piece of cake compared to having your play performed to a paying audience. And as for the sheer, sweaty palm inducing terror of sitting through an opening night of a play you've written, well, that has to be experienced to be believed.

But for some reason, I couldn't leave it alone. One play wasn't enough. One round of stress, of re-writes, of intense debate with actors, of worries about audience figures, of depression about reviews, of general self-esteem diminishing misery . . . I'd been hooked.

In the great tradition of the mountain climber, there's always another summit to attempt. No sooner are you down off one life-threatening peak, that you're off to find another, to further test your abilities and drive your loved-ones to distraction with worry.

So I sat down to write another play. This time, I had a little help from my friends, in that I got some actor colleagues to improvise and develop a story before I wrote. But essentially, the experience was the same. The same late nights huddled over the keyboard, the same beating of the thing into some kind of shape, the same assault on the nerves as the first night approached.

That play was Four Stories, a more modest success than its predecessor, but, nevertheless, a play with a beginning, middle and end; with characters, a plot and a theme, just like all the teach-yourself books recommend.

But still, with two under my belt, the need to carry on hadn't abated - although I had great difficulty in describing myself as a playwright. Playwrights are proper writers, who've had plays done at the Abbey, and wear suits - even the women. For me, writing was still something I did to fill the time between acting jobs.

It was only after the last one that I began to grow comfortable with the idea. That was because it was such an unqualified success, and because I only wrote half of it. The play was Scenes From a Water Cooler, and the other half was written by Paul Meade, my friend and partner in crime at Gúna Nua Theatre, the company we set up together to present our work.

People ask us how we did that. Well, we worked with actors to develop the story, we broke it down into scenes, and then we quite simply wrote half the scenes each. He did the odd numbers and I did the even. It was mad, but it worked, and it meant halving the fear factor as well.

But the crunch came earlier this year, when my daughter was born. The midwife was filling out the form for the birth certificate, and on it there was a box marked "father's occupation". I hesitated. Occupation? That's a thing involving commuting and two-weeks holidays and a briefcase, isn't it? That's pensions and bonuses and Christmas parties - I don't have any of that.

I looked at my wife, and back to the midwife. She was a kindly woman, but I didn't think she'd be up to a detailed description of the nomadic and random existence we theatre people lead. "I'm sort of," I began, "well, I've done a lot of acting, and I direct, but . . ."

And then it hit me. I knew that feeling. Somewhere in the back of my brain I could hear the faintest of voices, forming the very beginnings of a conversation; the tiniest spark of an idea: a man and a woman, arguing over a child. Where it came from, I'm not quite sure. I'm never sure. You can't be.

But I knew what it was. It was the beginnings of another play. It became Taste, and spare a thought for my nerves, as it opens tonight.

I looked at the midwife. "Playwright," I said. "Put down Playwright."

Taste, by David Parnell, opens tonight at Andrews Lane Theatre, Dublin, and runs until November 16th. To book phone 01-6795720