JK Rowling is on course to become the first billionaire writer, helped by the success of the film of Harry Potter and the Philosopher's Stone which has hung on to the top spot at the US box office and taken an estimated $188m (£132m) after just 10 days on release in North America.

The British author, who has sold 124m books worldwide, is now earning more royalties through merchandise than book sales. Harry Potter toys are expected to dominate the Christmas market, Ananova reports, and demand for a Lego version of Hogwarts Castle is so high that many shops have already sold out.

The film last week broke box-office records in the UK and the US and has now surpassed Toy Story 2's 1999 record to become the biggest grossing film over the American Thanksgiving holiday, Reuters reports.

In the US, the animated film Monsters Inc held on to second place, while new entries Spy Game, starring Robert Redford and Brad Pitt, and time-travel adventure Black Knight debuted in third and fourth place respectively.