The Harry Potter cast have become big stars since the first film in 2001
Harry Potter and the Half-Blood Prince, the sixth movie in the boy wizard series, is the fastest-selling DVD of the year, it has been announced.
Current figures show that 840,000 copies of the film, starring Daniel Radcliffe, sold in just a few hours.
John Stanley, of Warner Home Video, was "delighted by the extraordinary first day sales performance," he said.
However, the film did not break first-day sales record set last year by Mamma Mia! - which sold 1,669,084 copies.
The musical broke the previous record held by Titanic - based on DVD and video sales - by 560,000 copies.
The latest Harry Potter movie remained top of the UK and Ireland box office for several weeks when it was released in July.
Distributor Warner Bros said the film took more than $100 million on its first day of worldwide release.
The first movie in the series, which is based on the books by British author JK Rowling, was released in 2001.
Harry Potter and the Philosopher's Stone was a huge success and paved the way for the subsequent movies, with the final instalment due in 2011.
Meanwhile, US film The Hangover has become the biggest-selling comedy DVD of the year with total first day sales in the UK of 138,000.