During that summer I’d grown two or three inches - really sprouted up. Not all of the kids from my kindergarten were going on to Saint Agnes with me, and when I walked into class on my first day I was bigger than every other child. I panicked. I thought: “Oh, my God, I’ve flunked out - I’m back in kindergarten for another year. I am such a failure.” I ran out of the class, sat on the school steps and cried, wondering how I was going to break the news to my parents. This nun came up to me and said, in a strong Boston-Irish accent: “What’s the matter with you, dear?” Sister Rosemary was her name. She was quite old, with very white, wrinkled skin, and blue, blue eyes. I told her what was wrong. She smiled, laughed, sat next to me and put her arm around me. “No, it couldn’t be that you flunked, as you look like a very bright boy. What’s your name?” “Michael McShane.”

“Oh, you’re Irish. Is your father Ken McShane? He’s a lovely man. Don’t worry - you’re just bigger than the other children.” She walked me back to class, where I met my teacher, Sister Imelda (who was a terror). For the next four years Sister Rosemary would say “Hi” to me in the corridors and I’d sometimes make her a card. She called my mother once or twice and got to know her. She took an interest in me and my family and finally, in fourth grade, became my teacher, all day, for all subjects.

That year I hooked up with a guy named John Lyons, with whom I would eventually join the army. John was a charismatic person who could talk you into anything. On Fridays, Sister Rosemary would screen movies for us. With the lights off in the classroom, John and I would crawl out and roam the hallways.

One Friday, we went into the toilets and found an old, chewed-up cigar - and smoked it. The door opened and there was Sister Rosemary. “Why aren’t you watching, boys, it’s a good movie - and what’s that you’ve got in your hands?” I felt such a creep, ashamed. “Why are you smoking that thing? The man who smoked it first is the school janitor, and he has big, brown lips, like pieces of liver. That’s what your lips look like when you smoke. Not a good idea.” There was no hellfire preaching about sin from her when we did stuff like that. She was always able to influence me with reason, without adopting the tone of “I’m an adult, you’re a kid, so you’ll do what I say”.

She was very kind and reasonable in a system of religion that is often not like that with school kids. I mean, we had some rough-assed nuns at Saint Agnes. My dad was an army major and he said the nuns frightened him. The priests were like pussycats by comparison.

We read a lot of short stories with Sister Rosemary, even scary ones. When she set us an exercise she’d always read, not a textbook, but a piece of literature. She was very well read and may have come from a family of artists and writers. She truly had catholic taste, an ability to look at any work of art on its merits.

If I maintained classroom etiquette she would let me draw and would bring in pastels and crayons - things I didn’t have at home - and let me experiment. I would while away afternoons drawing and she’d suggest colours to me. I was good with shapes but not so good with colour. She took a liking to my creative mind, and, I realised later, she was trying to see where and how I could get better. She was one of those great teachers who pass information along, but you don’t know you’re being taught because they take such a subjective interest in you.

She used to let me read stories to the class on Friday afternoons, and encouraged me to read from the Bible in church. Whatever talents I had were encouraged and rewarded with more than just pats on the head. I lost touch with her when I started high school and got into my hard, trouble-making teenage phase, when no teacher could get through to me. But she would still occasionally go out to a cafeteria with my mother, and when I came home and was truculent, Mom would say: “Sister Rosemary asked today how you were doing.”

Even when I was in the army, I wrote her one or two letters and got letters back, but I never saw her again. She retired to an old nuns’ home in Saint Joseph, Missouri, which is where she died and was buried. I took a bunch of flowers to the grave a couple of years ago. She will always be my ideal of a very humane, powerful woman - the first woman I respected and loved as a person.

Mike McShane, actor and comedian, spent three years in the US army before beginning his acting career in California. Best known for his appearances on Channel 4‘s ‘Whose Line Is It Anyway?’ and as Friar Tuck in the film ‘Robin Hood Prince of Thieves’, he stars in the stage version of ‘One Flew over the Cuckoo’s Nest’, which is touring the UK until December (information: 08705 200 633). He was talking to Daniel Rosenthal.