I remember arriving at the Xaverian Missionary Fathers seminary for the first time. It was a Saturday morning and I took three buses from my parents’ house on the other side of Lanarkshire, which is a big thing when you are 12. I wasn’t very streetwise; I didn’t have a clue where it was and I didn’t have a map. When I got there, I walked up in the mist and saw some boys playing football on the grass in front. It felt like another world, like going back in time.

I was at primary school in Wishaw, Lanarkshire, when some Xaverian priests came to talk to us. They told us how they helped people abroad, building schools and hospitals. There wasn’t much talk about God, it was more about doing things. They were nothing like the priests I had come across before — they were Italian, for a start. I was used to Irish parish priests with a fairly narrow view of how you should live, so when these Xaverian fathers came in, well, we saw them like action men. So, when they said: “Come along on a Saturday morning,” that’s what I did.

In 1976, when I was 12, I started at the seminary to train as a missionary priest. It was an intense environment, a house chock-full with 90 boys. The first and second years slept in one room on the first floor, and the third, fourth and fifth years were in an identical dormitory above. The older boys didn’t need as much room, because people used to drop out or get kicked out. Of the 21 who started in the first year, there were only eight left by the fifth year.

The seminary was made up of two large, detached houses but, when the Xaverian fathers bought the buildings in 1958, they added school buildings and a sports centre. There was also a huge refectory, an aviary and a tarmac football pitch. I remember the corridors being lined with old photographs of Xaverian schoolboys from the late 1950s and early 1960s, which felt quite romantic. The place was in a bit of a timewarp but I found that quite comforting.

We lived in the grounds and didn’t go out, except to go home for the holidays or the occasional weekend, so it was like living in a bubble. We didn’t watch television or eat sweets and there were no shops — we had no money anyway. It was a safe cocoon, separate from the modern world. That was fantastic for me. I had found “normal” school harsh. I did well academically but I found it brutal. I got into fights at the seminary occasionally but there was no bullying.

My parents weren’t keen for me to go to the school, though my mum is a believer. She didn’t think (quite rightly, as it turned out) that I was cut out to be a priest. I don’t think they knew why I was doing it. Perhaps I didn’t either. I just liked the sound of it. As young boys, we all initially believed in God, but it was an unquestioning belief: that was the problem. As we got older, some of us started to think it might not be true but we almost never talked about God — we would have been too embarrassed.

My doubts came to a head when I was 17 and met a girl. She was a cousin of a classmate and I used to sneak out to see her, which was completely against the rules. I got caught and was given an ultimatum. It was a hard decision to leave because I had loved being there. But, deep down, I knew that I wasn’t going to be a priest, as I couldn’t do celibacy. It was inevitable that I’d leave, so meeting a girl just forced the issue.

The first play I wrote for the National Theatre of Scotland [Nobody Will Ever Forgive Us, which ran last November], was inspired by my time at the seminary. It was about coming back into the world after being cut off for five years, and not realising that flares were out of fashion and that everybody was wearing drainpipes. It started as a hobby, but I’m writing another play for the NTS, so writing is pretty much my day job now.

I don’t know what path I would have gone down if I’d gone to a normal school and I doubt I would have become an actor without going to the seminary. It shaped me. Having said that, in the five years I was there, I never did get to do any “action” stuff.

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