The seventh and final Harry Potter book goes on sale at a minute past midnight UK time on Saturday (July 21) -- 2301 gmt on Friday (July 20). Throughout the world, fans are expected to queue at bookshops, hoping to buy one of the first copies. It's a publishing milestone that ends months of fevered speculation among fans over the fate of the fictional boy wizard and his wand-wielding friends. In London, readers young and old are already in line with a long wait ahead. Many have dressed like their heroes for the grand finale of the Potter saga, which experts believe will be the fastest-selling book of all time. Author J.K. Rowling was an unemployed single mother without a publisher or agent 13 years ago, but is now the world's first dollar billionaire writer after the huge success of her first six novels and the Hollywood movies based on them. "Harry Potter and the Deathly Hallows" will hit the shelves in a carefully orchestrated release designed to maximise suspense and sales, from London and New York to Mumbai and Australia's Outback. But it has been marred by leaks of the contents of the book on the Internet, both real and fake, and by a mistake made by an online U.S. retailer that meant a small number of hard copies were sent to buyers days ahead of publication. One of the first to queue in London is Martin Meijer from the Netherlands. It's not the first time he's tried to be first to get the latest Harry Potter book. But on the last occasion he joined a line stretching for one and a half miles. He's ignoring all the spoilers and leaks and plans to read the last book in the series as soon as he gets it. Fans in central London feasted their eyes on sealed boxes containing copies of the coveted publication which began arriving at London bookshops mid-day on Friday. Araventhy Nanthanan, a self-confessed Harry Potter fan, says when she gets her hands on a copy she's going to "scream and run around". Another two fans from the Netherlands, Lenke Hanan and Renee Vloo, says they are just enjoying the experience of camping out in the centre of London. "It's like being part of one big family" said Lenke. But the big question on everyone's lips is what fate has J.K. Rowling in store for Harry? Some fans are resigned to the young wizard being killed off. "It's the final book so he probably has to die" said one.