Here's the new thread for posting quotes, with the usual rules:
- Please post all quotes separately, so that they can be voted up/down separately. (If they are strongly related, reply to your own comments. If strongly ordered, then go ahead and post them together.)
- Do not quote yourself.
- Do not quote comments/posts on LW/OB.
- No more than 5 quotes per person per monthly thread, please.
As far as I see, neither of the examples you linked provides any evidence that in 1939 it was incorrect to consider a British government assassination plot against Hitler as wildly implausible. The Oster conspiracy was an internal German plot, and the Foxley plan was just a proposal that was never approved nor carried out (and even as such, it occurred only after five years of a total war in which nearly all other centuries-old conventions of civilized warfare had been discarded -- a world very different from the one five years earlier).
Also, your Wikipedia link above fails to mention even a single assassination that would have been within living memory in 1939, and which would have matched the pattern of a government conspiring to assassinate a foreign leader. So if anything, it goes against your claims.
Successful assassination? Does that seem like the most relevant standard when it comes to the original question?
(On a side-note, the CIA seems to endorse the claim that Britain's SIS killed Rasputin. Surely we can trust the CIA...)