Amazon's day of reckoning: It's the return of Harry Potter

The release of the fifth Harry Potter novel, by author JK Rowling, is set to become the biggest ever ecommerce event and looks set to guarantee Amazon another highly profitable year.

In the first 24 hours of pre-ordering, Amazon.co.uk took 30,000 orders for the book and broke through the 250,000 mark at the end of May - a full three weeks before the official release of the keenly awaited fifth book in the series.

With just a few hours to go until the official release, Amazon.co.uk was reporting the final pre-order figure had topped 400,000 sales - making it the largest ever pre-ordered item in e-tail history.

A spokeswoman for Amazon.co.uk told silicon.com: "It's just unreal. In total there are more than 400,000 copies of the book leaving our dedicated warehouse today. To put that into some perspective that six times greater than the previous record which was Harry Potter and the Goblet of Fire.

"We've never seen anything like it. This release is the biggest ecommerce event ever"

Amazon.co.uk has been storing the books in a top secret location detached from its other warehouses and staff have been working through the night to ensure the pre-ordered books are despatched on time.

To put the numbers into perspective, if every one of the 400,000 pre-ordered copies were stacked one on top of the other, the resulting tower of books would be 25,200 metres tall. That's more than twice the height of Mt. Everest; 186 times higher than the London Eye or 106 times higher than Canary Wharf

The total weight of the books pre-ordered on Amazon.co.uk is 368 tons - the equivalent of a Boeing 747 Jumbo Jet or 53 large male elephants

Worldwide sales across Amazon's global properties topped one million.