Brady is translating the German translation of a English novel back into English. I could see where this would be an interesting way to have a gold standard to compare one's translation skills to, but then again I guess that depends on how much one trusts the original translator.
The Traitor's Gate, btw, is one of 13 novels that Edgar Wallace published in 1927, two less than the 15 he published in 1926. I remember reading somewhere that at the height of his career he had periods of dictating a book a week.
Update: The Wikipedia entry for Wallace is a good yarn in its own right. And, according to it, it's a book a weekend instead of week.