"20 years ago today a world that I had lived in alone was suddenly open to others. It's been wonderful. Thank you," she wrote on Twitter.

A pair of rounded glasses and a lightning bolt accompanied the social media site's special "HarryPotter20" hashtag -- a nod to the boy and a zigzag scar, who emerged from a cupboard under the stairs to become the world's most famous wizard.

20 years ago today a world that I had lived in alone was suddenly open to others. It's been wonderful. Thank you.#HarryPotter20

— J.K. Rowling (@jk_rowling) June 26, 2017

Joanne Kathleen Rowling had struggled through poverty before winning a £1,500 publishing deal with Bloomsbury to print 1,000 copies of "Harry Potter and the Philosopher's Stone".

The seven volumes of the saga have since been translated into 79 languages and have sold more than 450 million copies worldwide -- and those lucky enough to have bought a first edition of "Philosopher's Stone" have in their possession a collector's book worth thousands. 

"Harry Potter has had a huge impact on a generation of children, who became so obsessed with reading that they would queue for hours to get their hands on the next book," said Diana Gerald, head of the Book Trust, a charity which encourages youngsters to read.

Read also: Harry Potter turns 20: Business empire with humble start

Fans celebrate Pottermania

Events to mark the magical tale include a special exhibition at the National Library of Scotland in Edinburgh, the city where Rowling penned much of the first novel.

"J. K. Rowling wrote the books just opposite, and just down the road as well, so it's just really exciting to dress up and have some fun," said Francine Millard, 47, visiting the library in a Potter-themed scarf and carrying a toy owl.

Despite being just four years old when the first book was published, Kimberley Best said she was "obsessed" with Rowling's magical world.

"My life is heavily influenced by it, it just brought me out of a bad time so it's actually very important that I come and see it," she told AFP, referring to a "Philosopher's Stone" first edition on display filled with notes by Rowling. 

Curator Graeme Hawley said the book was on loan from a private collector for the library's "party" to mark a hugely important literary milestone.

"It's become disproportionately significant in terms of its reach into modern children's publishing, a total game-changer -- and the rest, as they say, is history," he told AFP.

Bloomsbury have published four anniversary editions of the first Potter book, in the house colours of Hogwarts wizarding school, while quizzes and crafts were the order of the day at libraries and schools around Britain.

St Paul's Cathedral in London on Monday published a video of music from the Harry Potter film series being performed at the famous site.

Pottermania over the past two decades has led to eight movies, a hit play and numerous spin-off books.

In October a "Harry Potter: A History of Magic" exhibition will open at the British Library in London, showcasing manuscripts and magical objects alongside Rowling's archives.

The Harry Potter empire has earned Rowling -- a committed philanthropist -- an estimated fortune of £650 million ($825 million, 743 million euros), according to The Sunday Times newspaper's 2017 Rich List.

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