Notice in the British "Show Boat" poster how Paul Robeson is billed just after Irene Dunne and ahead of Allan Jones, and pictured prominently. In the two American posters he is billed fourth and not depicted at all.
Robeson was a huge movie star in Britain and was treated there with uniform respect and admiration. A VERY different story from his life in the States, where besides 4th billing, he was just another 2nd class citizen. He was on his way to being branded as a Commie and blacklisted out of show business. No wonder he preferred life in Europe!