When the mural by Jack Hastings at Marx House in Clerkenwell Green in London was rediscovered in 1991 behind its library’s bookshelves, a film was made about the artist, his work with Diego Rivera in the United States, and how the mural came to be painted at Marx House in 1934.
I found a YouTube link in your post. Here are links to the same video on alternative frontends that protect your privacy: