“Here’s the amazing thing,” Henry Winkler, formerly the Fonz, tells me. “The books have been successful, very successful, in the US, but I could not sell them to television there. I couldn’t! And I tried every outlet! Producers would say to me, they’d say: ‘We love Hank! He’s very funny! But, look, kids love aspirational TV, and Hank… well, Hank has a problem.’” The pause here is a deliberately theatrical one. “…So I went to the UK, and sold them to the BBC instead! And guess what? It’s become one of the highest-rated shows for children on the channel. And that is not hyperbole, by the way. It’s fact.”

Winkler is referring to the Hank Zipzer series of books, now spanning 32 stand-alone titles since the first one was published in 2003, and which together have inspired three successful series on CBBC; a Christmas special, Hank Zipzer’s Christmas Catastrophe, screens next month. Zipzer is an ordinary 12-year-old living a fairly ordinary adolescent life, albeit one slightly hampered by the fact he has dyslexia. The dyslexia, says the show’s underlining message, will not, and does not, hold him back.

Winkler himself has dyslexia, but when he was school-aged – in the 1950s and 60s – the condition wasn’t yet recognised, much less understood. If you couldn’t read, couldn’t follow maths, you were stupid. Consequently, the actor, who grew up in tough New York, was considered stupid.

“It’s what I heard all my life: that I was stupid, that I’d never achieve anything,” he says, “and yet now here I am, talking to you, as a successful writer, actor, producer and director – and a father and grandfather. And I think I’ve done pretty well in all of them, right?”

For the past 13 years now, he has been visiting schools around the world, hoping to inspire those that might also be struggling. “When I tell them that they have greatness inside them, and that they are not defined by academia, they all sit up, their bodies become alert, and they go: ‘Holy mackerel! Do you mean that even though I’m not good at geometry, I might still be a smart person?’” He laughs out loud. “I tell you, watching their reaction – it’s like a gift from heaven. I love it.”

Winkler, now 71, is a celebrity of the old school, the consummate pro. Speaking to him is a highly entertaining endeavour largely because he puts so much into it; ours is less a conversation than it is me listening to a one-man show. We had originally arranged to talk via Skype, but his Skype is down, and so I call him at his Los Angeles home. He is aware, he says, that I will be wanting colour for my piece, and so he proceeds to offer some.

“Okay, so it’s 10 o’clock in the morning, my time, and I’m sitting at my desk between the living room and the kitchen area. Let me tell you, it’s a delicious area, because the kitchen right now is full of food as we’re getting ready for Thanksgiving. The smells! Oh look, my dog has just walked by.”

The man fizzes like a carbonated drink. It’s as if the success of Hank Zipzer has given him a second wind – and well it might have. Though American TV gave Zipzer the cold shoulder, the UK has embraced him and its message. As a consequence, it has transformed Winkler into an inspirational spokesman. In 2011, he was awarded an honorary OBE for services to children with special educational needs.

“I’ll never forget the phone call I got from the Queen’s representative here in Los Angeles asking whether I would accept it,” he sighs. “I said I would think about it, and I did, for like a second!”

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The successes he has achieved throughout his career are clearly all measured against his adolescent failures, and have helped him construct a self-confidence that was sorely lacking in childhood. His father, the president of a lumber company, forever struggled with his son’s poor displays at school, and Winkler has suggested that their relationship was a strained one. The character of Mr Rock in Hank Zipzer, a maverick music teacher, is based on Winkler’s own music teacher, the only adult that ever offered the young future actor hope.

“He said to me one day: ‘Winkler, you know what? You’re going to be okay.’ I held onto that sentence like Leo DiCaprio held onto that piece of wood when he slid off the boat in Titanic.” But DiCaprio’s character ultimately died, frozen to death in the freezing Atlantic; Winkler, on the other hand, thrived.

A jobbing actor in the early 1970s, he landed his defining role in Happy Days – a forcefully cheesy, if undeniably feel-good, US TV sitcom that also featured a young Ron Howard, now one of Hollywood’s biggest directors – in 1974. The Fonz was the cool “kid” whom all the others admired and envied: for his motorbike, his leather jacket, his way with the ladies. The fact that the Fonz was a good decade older than the high school children he hung around with was barely commented upon in the series; were it to be remade today, the Fonz would probably be hauled in by the police for questioning.

While the show was modestly successful in the UK, it was a cultural phenomenon in the US, Winkler a latter-day James Dean for the TV-dinner generation. He enjoyed the attendant spoils of his fame, but unlike his small screen character, he managed to settle down, marrying his girlfriend Stacy Weitzman in 1978, with whom he has two children. Happy Days ended in the mid-1980s, and Winkler went on to appear in further sitcoms, among them Parks and Recreation and Arrested Development. In 1993, he directed Burt Reynolds in the film Cop and a Half.

His workload today, he suggests, has never looked better. He recently appeared in what he tells me was “the highest rated [US] show of last summer”, Better Late Than Never, an I’m A Celebrity-lite travel show in which he, Star Trek’s William Shatner and former boxer George Foreman, travelled throughout Asia eating pork vagina and bull penis soup. Next year, he will be seen in the HBO mockumentary Barry alongside Trainwreck’s Bill Hader.

“You know, being an actor is like being a brain surgeon,” he muses. “When you’re 55, you finally put it all together. I was 27 years old when I got the Fonz, but it’s only recently that I arrived at where I always wanted to be as an actor.” Little wonder, then, he sounds quite so energised.

“And the energy is not manufactured!” he roars. “I’m telling you straight: I am blessed! I love my life! My only real concern is – no, not death – but the fact that one day I will not be able to call upon this endless stream of energy, because what then? What then?”

‘Hank Zipzer’s Christmas Catastrophe’ is on CBBC on 22 December at 09:05am, Christmas Day at 7pm and Boxing Day at 3:30pm