Since 1997 author Lee Child has been overseeing the world of Jack Reacher. There are the novels, of course (one released almost every year, now mostly written by Child's younger brother Andrew) and a pair of Tom Cruise movies (in 2013 and 2016).

"That was the thing that I thought, 'How are they going to do this?'" the author says.When the main character trait of the titular hero in Reacher is that he's just really freakin' huge, how do you challenge him physically?