Going in circles
One possibility is that he had secret centrifuges. (this is pretty unlikely, don't you think?)
One possibility is that he was *not* in fact shopping for yellow cake.
One possibility is that he was shopping for yellow cake without the ability to do anything with it.
Sherlock Holmes was generally against jumping to conclusions. How is this for logic: since we just had a war [war being as extreme a lesson as I can think of] based on jumped conclusions, and conservatives have not learned anything from the experience, I conclude that jumped conclusions are a necessary part of their thought process.