A different chapter begins for the star who put his unhappy days behind him

While other cast members immediately flicked through the pages to see how many lines they had been given, Winkler's copy was stuffed in his bag, only to be read when no-one else was around.

He'd had difficulty reading ever since he could remember and, having landed the dream role straight from drama school, he didn't want to give the director any reason to let him go.

Arthur Herbert Fonzarelli was originally written as a bit part, but the Fonz quickly became the reason why millions tuned in each week. Adulation and bags of fanmail followed, but most of the time Winkler was too busy feeling like a fraud to even think of living the dream.

"The Fonz was everything I wasn't," he says, the New York drawl still instantly recognisable. "He was the kid everyone

wanted to be. He was the kid I wanted to be, but inside I was just a big bowl of gelatine. I worried about not getting a girlfriend and I worried about having to read scripts aloud in a group. Before anyone asked, I would take them home and memorise each line off by heart."

Winkler was dyslexic, but growing up in the 1960s it was a condition that no one paid too much attention to. In his school reports, he was simply described as lazy and uncooperative and at home his parents couldn't hide their disappointment.

"They hoped for an academically gifted son and instead they got me," he says. "I was the headmaster's worst nightmare. When a teacher read a book, I would act it out. I was the typical class clown and was never far away from detention.

"I was in the bottom three per cent at school and like so many people who have dyslexia, I was told I would never amount to anything. My parents were incredibly strict and I guess they thought that if they just kept telling me off I would change. I didn't and neither did they."

It was only when Winkler's stepson, Jed, was diagnosed dyslexic, that he realised he was too. By that time he was 31 and, while he had already proved his early doubters wrong, it finally allowed him to draw a line under the feelings of low self-esteem which had followed him from childhood.

"I'd never stopped moving forward," he says. "I was like one of those children's toys with sand in the bottom. Whenever someone knocked me down, I would pop right back up again. But although I was resilient, the idea that I was stupid was always lurking in the background. When you say to a child young enough and often enough, 'you're lazy, you don't work hard enough', eventually they start to believe it."

It was only a few years ago that Winkler, now 64, began to wonder whether his own experiences might help other children. The result has been a series of children's books featuring a young dyslexic schoolboy. Written with Lin Oliver, Hank Zipzer is a thinly veiled version of Winkler and the series, which has already sold 2.5 million copies in the US, is about to be published in Britain.

"I love acting, but what I'm most proud of is the books," he says. Winkler is in the middle of a UK tour of schools and next week he will be guest speaker at the Children's Media Conference in Sheffield. Most of those he's met have never heard of Happy Days, but he admits there's been a fair few parents squeezing into the back row of the assemblies.

"Until I was in my 30s, I had never read a book. Now every time I finish one I carefully place it on my shelf as a reminder of how far I've come. But you know reading is one thing, writing is something else altogether. It has given me more joy than I ever thought possible."

Winkler is blessed with those peculiarly American traits of endless enthusiasm and boundless optimism. While still acting and directing, his work as a children's rights campaigner takes up increasing amounts of his time. A new series of books about a boy and his imaginary friend are in the pipeline and as well as being involved in numerous children's charities back home, he also does work with the UK Teaching Awards.

"There has been a tremendous surge forward in terms of schools understanding the whole child," he says. "But there are still so many teachers who are so overwhelmed by the size of classes and by trying to teach the same material to the fastest child and the slowest that many slip through the net.

"However, what I've seen and what I've heard from the most innovative teachers does give me hope. There was one who said if she finds herself hitting her head against a brick wall because one of their pupil's just isn't getting geometry, she gives them in a test something they can do.

"To me that makes perfect sense. A child flourishes when they realise there are things they are good at. It allows them to relax and ace the things they find difficult.

"When children become frustrated with the school, it's almost like they stop still. If they feel they are a failure then more often than not they will decide to make a name for themselves in some other way. Either they become difficult or they try to blend into the wallpaper."

Winkler talks of his dream of seeing schools introduce courses on building campfires and growing vegetables. It's the kind of idyllic talk the educational establishment has grown weary of, but what he means is the return to a system which values vocational skills as much as academic ones.

"The winter just gone I was doing panto in Liverpool and I met the daughter of the man who drove me to the theatre," he says. "She was nine years old and incredibly bubbly. One day she told me her teacher had said, 'Come on now, Anabelle you really should know this stuff by your age'.

"My heart went out to her. She wasn't a troublemaker and she was obviously bright. Unfortunately, she didn't fit into the narrow expectations some schools have of their students. I sometimes wonder how much talent is being wasted and how many hopes are being snuffed out."

Now nearing the end of his school's tour ,Winkler is looking forward to going back to the States. His 38-year marriage to Stacey Weitzman has been one of the most enduring in showbusiness and family life has always been important. Jed has just directed his first film starring Uma Thurman, younger son Max works in the computer games industry and daughter Zoe, who is also dyslexic, now works as a teacher.

"I can never understand a parent who is disappointed when their child fails to live up to some educational ideal," he says. "They seem to forget that their son or daughter shares their DNA. My own parents were unapproachable and I made a deal with myself early on that if I ever had kids I would be a very different father.

"I hope I have kept my word. I'm proud of my three kids simply because they breathe. My children are very good breathers."

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Henry Winkler will be speaking at the Children's Media Conference in Sheffield on June 30. For more information visit www.thechildrensmediaconference.com