He's a stand-up who specialises not only in doing shows for children, but in helping them to be performers in their own right.
I saw his Comedy Academy 4 Kids in action on a Sunday afternoon at the Pineapple dance studios in London's Covent Garden. The flavour of the session revealed itself when, five minutes after the start, the door crashed open and a 10-year-old boy entered in a sprawling forward roll, ending up spreadeagled on the floor. No one took much notice, so he got up without comment and joined the others sitting on the floor listening to James.
Showing off, you see, is what the Comedy Academy is about. "Stand-up comedy is a rather selfish, arrogant discipline," says James Campbell. "It's about saying, 'listen to me!' And I've got 15 class clowns in the same room."
His aim is to help each child develop a three-minute comedy spot which they'll deliver at his Comedy Club 4 Kids at the Menier Chocolate Factory, not far from Tate Modern. "I want each of them to be able to talk about the world from their own point of view," says James.
This means moving them beyond what the whole group has learned to call "Christmas cracker jokes" and into their own stories. So from one child we have a mock-weary monologue about a family visit to the zoo which he found boring. "Why don't they put the sharks in with the tuna? Now that would be an interesting zoo."
And nine year old Max speculates on mixing up characters from different films, visualising Edward Scissorhands attempting, with disastrous results, to climb the ship's rigging in Pirates of the Caribbean.
The confidence-boosting value of all this is plain to see. Max's mother, Wendy Klein, says: "It's been exactly the right channel for him. It suits his quirky talent and ideas better than a conventional drama group".
For a teacher, there's much to learn in one of James's sessions. It's an impressive demonstration of what happens when you just encourage children to tell their own stories in a supportive group.
Key stage 1 teacher Caroline Morris, who's seen James Campbell working with children in her school - St Ebbe's primary in Oxford - says: "I learned a lot - about telling stories before writing them down, for instance, with the children listening and learning. We often tell the children that's how stories began, but we don't have the confidence to do it ourselves."