The writer comes in at number four thanks to the film adaption of her racy debut novel, which broke U.K. box office records upon its release earlier this year (15).

The remaining books in the trilogy, Fifty Shades Darker and Fifty Shades Freed, are also set to become movies with stars Jamie Dornan and Dakota Johnson. James' husband Niall Leonard will pen the screenplay for the second film.

Harry Potter author J.K. Rowling remains top of the list with $850 million (£530 million), followed by Barbara Taylor Bradford and Lord Archer. Jackie Collins and Ken Follett come joint fifth.