First Hallow for the new Harry Potter book cover

Harry Potter and the Deathly Hallows, the final installment in city author JK Rowling's series, is set to be published on July 21.

The cover illustration for the children's edition is by Jason Cockcroft, who drew the cover illustrations for the previous two Harry Potter books.

Inevitably, Rowling fans will scrutinise both it and the adult jacket for clues as to the novel's contents.

The illustration shows Harry, now in his seventh year at Hogwarts, with friends Ron and Granger, raiding what appears to be a treasure trove.

The adult edition's cover design is from a photograph by Michael Wildsmith, who has photographed all the adult edition jackets.

The image shows a gold locket engraved with the letter S, apparently leaving devoted Potter fans with few clues as to the novel's content. It is rumoured that one of the main characters, possibly even Harry himself, will be killed in the book.

The covers will be used throughout the world on the English language editions - apart from in the United States.

Cockroft, who has worked on other book covers for Bloomsbury, also drew the illustrations for Harry Potter and the Order of the Phoenix - at the time the fastest selling book in publishing history - and for Harry Potter and the Half-Blood Prince.

When he designed the cover for the Order of the Phoenix, Cockroft was not allowed to read it before he set to work - such was the secrecy surrounding the 2003 novel.

Rowling announced in February that the seventh and final book, Harry Potter and the Deathly Hallows, would be released at midnight on Saturday, July 21.

The book had already shot straight to number one in the Amazon chart, just eight hours after customers were first offered the chance to reserve a copy on December 22 - the date when Rowling first confirmed the title.

It is expected to tie up the loose ends of the story which first began 17 years ago, when Ms Rowling started writing Harry Potter and the Philosopher's Stone in an Edinburgh cafe.

Although details of the new book's plot have been scarce, she has hinted that a main character, possibly Harry himself, is to be killed off.

The Royal Mail has already begun gearing up to hire the extra vehicles and staff to deliver the new novel.

There was more good news for fans earlier this week, when Warner Bros confirmed that Daniel Radcliffe, Rupert Grint and Emma Watson have all signed on to reprise their roles as Harry, Ron and Hermione in the final two films in the series.