Price war declared over new Harry Potter book

Kwik Save, the food chain, led the discounters with an offer to sell Harry Potter And The Half-Blood Prince at £4.99, against its cover price of £16.99.

Britain's biggest store chain, Tesco, will sell the book for £7.95, a penny cheaper than rivals Asda and a pound cheaper than Sainsbury's. Internet sites such as Amazon.co.uk are also drastically undercutting independent bookshops, many of which are selling the title at full price.

The sixth instalment of J K Rowling's wizard saga is expected to be a financial bonanza for its publisher Bloomsbury and the book trade predicts it could become the fastest-selling title in history.

Two million copies are expected to be sold in the UK and 10 million worldwide in the first 24 hours alone. Up to 300,000 customers had been expected to cram into bookshops at midnight last night, when the book went on sale. Many shops were throwing Potter parties and the bookseller Ottakar's changed its name to "Pottakars" for the occasion.

Rowling launched the title at Edinburgh Castle in a ceremony that featured fire-eaters, torch-throwers and jugglers. Two thousand children aged eight to 14 watched Scotland's best-known author enter the castle on a red carpet. Inside were 70 cub reporters from around the world who had won competitions to attend the choreographed marketing event.

Interest in the book has been heightened by Rowling's disclosure last year that she would kill off a character; speculation centres on Hagrid, Professor Dumbledore and Harry's Uncle Vernon.

The first five Harry Potter books have sold more than 265 million copies in 200 countries and have been translated into 62 languages, making it a worldwide success. The series is the biggest merchandising phenomenon ever, generating more than £1bn from toys and other licensed goods.