A 10-million pounds security operation featuring an army of guards, satellite tracking systems and legal contracts has swung into action to prevent any leak of details of the seventh and final Harry Potter [Images] book.

As millions around the world eagerly await the release of Harry Potter And The Deathly Hallows on the midnight of July 21, only its author J K Rowling and about 20 other people, including the book's editors and illustrators know Harry's fate.

When the finished manuscript was taken by hand from London [Images] to New York, the lawyer for the American publisher, Scholastic, sat on it during the flight. With each successive Potter book, the security has grown. Nothing has come close, however, to the arrangements for the finale, The Sunday Telegraph observed.

London-based Bloomsbury, which publishes the Potter books in Britain, has hired secure sites across the country to house the book prior to distribution early this week. It is understood that several dozen security teams will protect the sites round the clock. Experts say security staff will earn up to 30 pounds an hour with a guard dog, up to 20 pounds without.

Print factory workers in Britain have been threatened with the sack if they leak any details, while German publishers banned mobile phones and even packed lunches in the printing plant. Some employees reportedly had to work in near-darkness to prevent them reading the book.

It is from Tuesday, however, when copies begin to be sent out to retailers, that the most crucial part of the security operation will come into effect. The trucks Bloomsbury will use are fitted with satellite tracking systems costing up to 1,000 pounds each, which will reveal whether any of the vehicles deviate from their intended route. The books are on sealed pallets fitted with alarms to prevent tampering.

At one of the world's biggest booksellers, Barnes and Noble in America, the books are being kept in padlocked trucks at the insistence of Scholastic. Amazon, the online retailer, has cordoned off special sections of its warehouse to ensure restricted access.

All retailers have had to sign a legal embargo preventing them from divulging any of the book's content or selling copies before the release time.

A spokesman for Borders, the bookshop chain, said, 'We agree not to open any of the books before midnight. We can't even line the shelves before then.'

A spokesman for Bloomsbury said: 'We have a litigation specialist poised 24 hours a day, seven days a week to deal with any breaches. It is our intention to enforce the embargo vigorously and seek an immediate injunction if required.'

While experts put the cost of all this at 10 million pounds, the lengths to which publishers have gone are not surprising.

Four years ago, Donald Parfitt, a forklift driver from Suffolk, was ordered to do 180 hours community service after he admitted stealing pages from Harry Potter and the Order of the Phoenix from the printing plant where he worked. Last year, one Aaron Lambert was jailed for four and a half years for stealing copies of Harry Potter and the Half-Blood Prince and trying to sell them.

In recent weeks, Rowling has reportedly received letters from people asking her to reveal the ending of the seventh book because their terminally-ill relative may not live until Saturday.

Booksellers expect record sales for a number of days. Jon Howells, a spokesman for the Waterstones chain said: 'Everyone wants to find out the ending for themselves. They don't want to hear it second-hand. Putting The Da Vince Code against this book is like putting a bungalow next to the Great Pyramids."