Technically speaking, they almost don't! The Wimsey Papers were published as articles in 1939-40 in The Spectator, and have not been published as a collection*. The ebook I have is an online work of public archival activism - someone literally pulled together the physical back issues of The Spectator and transcribed them. I am happy to share them!

*In fact, the transcriber claims that The Spectator's archives only go back to 1960s, which may have been accurate then but does not seem true now - I was able to see the Wimsey Papers in a search on the archives website, tho I could not access them without purchasing a subscription