John Wayne and Kirk Douglas never saw eye-to-eye politically, as the latter once confessed in a TV interview.

Duke considered Spartacus to be Marxist propaganda and was infuriated by his liberal co-star when he was once late to set when filming The War Wagon together.

It turned out Douglas had been shooting a commercial to endorse Edmund G Brown, a Democrat, as Governor of California.

This enraged Wayne, a life-long conservative, who was late himself the next day as he’d been filming an advert to endorse the Republican candidate, fellow actor and future US President Ronald Reagan.

Yet the Hollywood stars avoided talking politics and became friends, with Douglas praising how professional and hardworking an actor Duke was.

In 1976, Wayne’s final film The Shootist, in which he played an old cowboy dying from cancer, was released. During the shoot, Duke was hospitalised for two weeks with influenza and at one point it was uncertain if the movie would even be completed as the star’s doctors almost forbid him from finishing the filming.

Nevertheless, the tenacious 69-year-old managed to push on through to the end of production, and the movie was met with positive reviews. In fact, it was so good that Douglas wrote to Wayne to congratulate him.

The letter read: “Dear John, I saw The Shootist. You were terrific, you S.O.B. As a matter of fact, I think it was one of the best performances you’ve given in a long time. Great simplicity, great depth, wonderful ironic humour. Of course there were some thing I would have done differently, but I certainly enjoyed the film. All my very best to you. Kirk Douglas.”

A few weeks before he died of stomach cancer in 1979, John Wayne’s 72nd birthday was marked by him being awarded the Congressional Gold Medal. This was after fellow Hollywood stars, including Democrats like Douglas, supported the award with statements praising Duke as an American icon and patriot.

Douglas wrote: “I strongly believe that John Wayne should receive the Congressional Medal of Honor. He is an authentic chunk of Americana. His personal and artistic life represent the best qualities of America admired by people around the world. He has always been a strong force for the American way of life. He has personified that force privately and artistically for many, many years. The world would applaud - the action of bestowing this medal on a great American.”