His Sunday evening radio programme was designed to rally morale among the population and was one of the most popular of the period.
But in early 1941, eight weeks into its latest run, the broadcasts came to an end and were never resurrected, prompti
ng much speculation over what had happened.
Now, almost 65 years later, Priestley's stepson believes he has the definitive answer and will bring an end to the mystery in a lecture next month.
Nicolas Hawkes, who lives in Ilkley, has pieced together the answers by scouring the BBC archives and other documents from the time.
He said his stepfather had never spoken of the incident in later years despite the controversy at the time.
But Mr Hawkes, a retired lecturer, believes the evidence suggests Priestley's scripts finally prompted elements of the political establishment to take action.
While his broadcasts were hugely popular their content did not always go down well with a certain section of British society at the time.
Mr Hawkes said: "He was a bit left of centre in outlook, not really in the political sense but in that he believed very strongly in community, in justice and in saying that Britain couldn't go back to the injustices of the 1930s and the men and women involved in the fighting must be given a good deal when the war was over.
"Winston Churchill would not put his mind to what kind of society we should have after the war. There were Conservatives who said 'never mind about society, never mind about justice or how to improve life for people, we just want to win the war'."
Priestley was given the job in the early years of the war when the BBC was looking for broadcasters who could raise morale.
He began his broadcasts in the wake of the evacuation of forces from the beaches at Dunkirk and stayed on the airwaves for 20 weeks.
Mr Hawkes said: "He had a gift for language and a gift for communication and a record as an infantryman in the First World War. He was a person who could reach people across the country and had a very good microphone voice, very deep with lots of tones.
"He was hugely praised and admired by all and sundry. People used to say that Churchill was the only person more people listened to than Priestley.
"The broadcasts were aimed at people at war but they weren't about the war. He was really talking about his experiences and his observations of people.
"When he came back in 1941 after his break, his listening figures went up from 32 per cent of the adult population to about 40 per cent, his highest being 44 per cent.
"Graham Greene, as a writer, did not rate Priestley highly but he wrote in the Spectator that Priestley had become a national figure and had held the country together."
As for the exact way Priestley was removed from the airwaves, Mr Hawkes will wait for his lecture to the JB Priestley Society to reveal all. The lecture will be held at Bradford University on Saturday, March 18.
