How does Priestly use Dunne's theory of time?

Time, which deeply fascinated Priestley, is a central theme in many of his works. He famously was interested in Dunne’s theory of time, which argued that the past was still present, and that time was not linear as many traditional accounts suggest. An Inspector Calls explicitly deals with the nature of time in its final twist: has the play, we might wonder, simply gone back in time? Is it all about to happen again? How does the Inspector know of the “fire and blood and anguish,” usually interpreted as a foreshadowing of the First and Second World Wars?