News, views and top stories in your inbox. Don't miss our must-read newsletter Sign up Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

It was the year of Labour’s landslide victory, the Spice Girls dominating the charts and Titanic sailing into box ­office history.

But 1997 also introduced us to the phenomenon of Harry Potter , the boy wizard whose adventures still have readers all around the world spellbound.

Author JK Rowling published the first book in her seven-part series, Harry Potter and the Philosopher’s Stone, 20 years ago this month.

And within two decades, the orphan with the lightning scar on his forehead has gone from living under the stairs at 4 Privet Drive to being a £19billion franchise – with no sign of slowing down.

As well as the books, films and theme parks, Hogwarts’ favourite son has waved his wand in the West End. The play Harry Potter and the Cursed Child won an unprecedented nine Olivier Awards.

There is also the successful Pottermore website, the merchandising and, of course, the second film in spin-off series Fantastic Beasts, starring Eddie Redmanye, entering filming soon.

(Image: Getty Images) (Image: Â©Warner Brothers Intl Television)

So as the boy wizard hits the big 2-0, what is it about him that keeps us muggles under his spell?

“I would say you can expect your grandchildren to be waiting in line to see new film adaptations in 50 years and beyond,” says John Granger, the US-based author of Harry Potter’s Bookshelf and possibly the only person in the world writing a PhD on the hero.

“When people talk of popular literature a century from now, they will call this the age of Rowling, as today we talk about the age of Dickens. But, given that Warner Brothers own the rights to adaptations, I think we’ll probably see reboots and spin-offs even after Rowling is no longer with us.”

The reason to expect such longevity begins with the books themselves. “They are brilliant stories,” says Sue Wilkinson, boss at The Reading Agency charity.

(Image: PA)

“They are full of adventure and twists. We recently completed a survey and Harry Potter was still top among 16 to 24s, and the reasons were fascinating. One of the biggest was the books show it’s OK to be different and struggle with how you feel. There is that element of teenagers battling evil but then it addresses real issues. It speaks directly to ­children and young adults.”

The story of how Harry came to be is almost magical in itself. Rowling was a single mum on benefits when she dreamed up Harry while waiting for a delayed train in 1990.

She began writing every day, going to two local coffee shops in Edinburgh. In 1995, she sent the first manuscript to 12 publishers, all of which rejected it.

(Image: Warner Bros)

But a year later, she had a stroke of luck. Bloomsbury accepted it on the advice of Alice Newton – the eight-year-old daughter of one of the bosses. The firm released 1,000 copies on June 26, 1997 and swiftly realised it needed more. Five years later, Rowling was worth £238million. Today, she is worth around £600million.

Her skill has been in growing the series with her audience. If the first book was aimed roughly at eight-year-olds, the last – a decade later – was aimed at older teens.

Themes were darker, feelings more complex and violence more explicit. There was teenage angst thrown in.

“To be able to move with your audience like that, while remaining true to your original stories, is the skill of a truly great writer,” says Wilkinson.

(Image: Handout) (Image: PA)

Perhaps just as important has been the subtle way Rowling, 51, appealed to both genders. Harry is male because little boys, she realised, tend not to read about little girls. “But girls read between the lines,” says Susie Winter of The Publishers Association. “They understand that Hermione – and Ron too – is every bit Harry’s equal and feel included in the adventure.”

As the stories grew darker, Bloomsbury released the books with adult covers to affirm that the appeal crossed generations as well as genders.

“This was an exercise in signalling,” says Susan Gunelius, author of Harry Potter: The Story Of A Global Business Phenomenon. “It almost gave permission for mature readers to buy them.”

Nor was this the only marketing wizardry. Rowling has kept tight control over merchandising to protect against overkill and brand backlash.

(Image: PA)

She refused to become involved with firms she felt would over-expose Harry – or did not fit in with her ethos, like McDonald’s. Rowling would not allow her creations to appear on the burger chain’s Happy Meals.

“This is a huge thing for an author to turn down,” says Gunelius. “The result is fans respect the integrity and it reaffirms their love for the brand. It ended up being a very smart move.”

By reducing exposure in this way, each new release is still met with a clamour that ­borders on fever pitch. “Even snippets of news cause huge amounts of excitement,” says Gunelius. “Then the hype becomes self-generating.”

Universal has opened Wizarding World of Harry Potter lands in Florida and California, and Warner Bros runs a studio tour in North London. The films – which launched the careers of Daniel Radcliffe, Emma Watson and Rupert Grint – grossed £6billion at the box office. This makes it the second-biggest film series, after the Marvel Cinematic Universe.

Some people believe the power of Potter was also down to timing. It was the book of choice for the first generation of children who never knew a world without the internet. When they wanted to talk about their loves and passions, they did so online.

(Image: 2009 Warner Bros)

“Peer to peer and word-of-mouth recommendation is the most powerful selling tool there is,” says Gunelius. “And these kids didn’t just tell the rest of the school about this great book, they went online and told the world.”

But according to Julian Harrison, curator of the upcoming Harry Potter: A History of Magic exhibition at the British Library, there is one final, over-riding factor to consider. The stories, he reckons, tug deeply on our psyche because they are mined from myths and folk tales we know already.

“With these folk tales – such as the existence of unicorns – we know they have some appeal because they have been repeated down the ages,” he says.

“So Harry Potter takes these legends and superstitions and repackages them. Like how the mandrake plant screams when it is plucked during the Hogwarts herbology class. This is actually an ancient superstition.

“But the way these things are weaved into these modern stories gives them a new life. The stories feel fresh but you could say it’s in our DNA to like them. And that is the genius.”