Each book weighs 1kg, and as health and safety regulations at Royal Mail permit postal workers to carry a maximum of 16kg of post, the number of books a postman can carry will be limited.
However, instead of drafting in a parliament of owls to deliver the books to eager Harry Potter fans, Royal Mail is putting on extra delivery vans to cope with the books.
A second problem lies in the fact that, at 768 pages long and over 6cm thick, the book, 'Harry Potter and the Order of the Phoenix', will not fit through most letterboxes in the UK.
Reports say that around 500,000 copies are expected to be delivered across the UK, and 8.5m have been printed around the world.
A Royal Mail spokesperson said: "We have plans in place to ensure a successful delivery and to avoid disappointment. It's a big operation but the Royal Mail is used to big operations."
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