Worldwide sales of the five Harry Potter books have reached the 250 million mark. Miss/Mrs JK Rowling's agent, Christopher Little, confirmed the news on Monday - and revealed Rowling had began work on the sixth Potter adventure.

The series has been distributed in more than 200 countries and translated into 60 languages from Hindi to Ancient Greek.

The fifth book, The Order of the Phoenix, sold 1.78 million copies on its first day in the UK alone.

Mr Little issued a statement via Potter publisher Bloomsbury that the series had "entered the guinness books yet again" with a "record-breaking, unprecedented streak of worldwide sales" of 250 million.

Teachers and publishers acknowledge that the Potter books have been instrumental in turning more children on to reading.