Welsh writer Ken Follett is thought to have earned a net worth of $55 million (£41.4m) from his historical novels. His debut novel Eye of the Needle was published in 1978 and he's since written more than 30 books, selling over 160 million copies around the world.

The University College of London graduate has topped The New York Times Best Sellers list numerous times and at least six of his novels have been adapted for film or TV. Follett even had a cameo appearance in two, despite having been forbidden from watching TV by his religious parents as a child. The rights to The Third Twin were reportedly sold to CBS for a then-record $1.4 million (£1m) in 1997.