If my book is turned into a film, how much money will I make?

If my book is turned into a film, how much money will I make?

Derek Johns (Managing Director - AP Watt Literary Agency) gives expert video advice on: Will an agent sell my book rights to Hollywood?; How many books make it to the screen?; If my book gets optioned, will I get to write the screenplay? and more...

Option payments are obviously very small, generally no more than a few thousand pounds. If a film actually reaches the screen, cinemas, the the author can figure to make a six figure sum.