Piece here by the author of the likely source material for the Daily Mail’s attack on Ralph Miliband.
“The Miliband family were Jews living in Belgium who had arrived in May 1940 after fleeing persecution from the Nazis who had recently taken over western Europe. Ralph was shocked by the level of anti-Semitism that existed in England at the time. Ironically, much of this anti-Semitism and dislike of Europeans had come from the propaganda campaign that had taken place in the 1930s. The man behind this campaign was Lord Rothermere, the great-grandfather of the current Lord Rothermere, the owner of The Daily Mail. ”
There’s more about Rothermere’s quite extensive involvement with Nazism.