Comedian Carl Donnelly with Kangaroos' at the Melbourne Zoo.

Eye-to-eye: Carl Donnelly was surprised to learn kangaroos are real. Photo: Justin McManus

Australia seems to have loomed large in English comedian Carl Donnelly's life, even though he's only visited for comedy festivals.

A month at the 2013 Adelaide Fringe culminated in his decision to turn vegan. A couple of months later at the Melbourne Comedy Festival, his lifelong understanding that kangaroos were imaginary animals was suddenly shattered during a visit to the zoo. And it was in Melbourne - although this is going back a few years now - that he came up with his favourite joke.

It came to him, he says, while he was sitting in the back of the Capitol Theatre. It doesn't really matter what the joke was about; suffice to say it involved shellfish and food poisoning.

What he liked about it was that he told a story that went for seven minutes without a joke until the final punchline; the audience just had to trust it would be worth it. It was scary, he says … but it remains his favourite routine because he has never seen another comedian structure a story that way. "Mostly, no one's style is that different," he says. "You're just talking about stuff and get a laugh. But sometimes, something comes out of the blue."

Donnelly is 32. He says he came late to stand-up; he was 21 when a friend took him to see a little-known comedian called Addy van der Borg in a small South London club. That was his eureka moment. "I never knew what I wanted to do," he says, "but I always had ideas constantly going round my head." He had kept notebooks and written sketches at school, then tried studying film production, but realised that wasn't what he wanted - it took so long to get a film up and running.

"But stand-up is instantaneous," he says. "You can write an idea on a piece of paper and do it at a gig that night." The fact that it also has to be funny is a bonus. "I want to talk about something that's personal, but I also want to be really silly and funny with it … that's my nature."

Even so, he doesn't dodge issues. The arguments for gay marriage are so obvious it seems merely hectoring to restate them, but he sends up homophobia engagingly by suggesting all men ought to be gay, given that "all sex is disgusting; it's just one second at the end that's quality". It's soft as social commentary goes. Even so, he's had walkouts. Which leads, of course, to a discussion of the things he wouldn't actually ever find funny, like the disturbing rise of the rape joke.

He realised he crossed a line, he says, when he was separating from his wife and talking about it on stage.

"For a little while I had some material about the frustrations of being in a relationship that's failing. I think I was in a bad place and it actually sounded quite misogynistic … As soon as I realised, I got rid of it so it sounded more like I was a dick."

Carl Donnelly is part of the Best of the Edinburgh Fest at RMIT Capitol Theatre until April 20.