Not their penchant for torture, lies and secret evidence which have been well documented in recent years, but their sheer historical propensity for idiocy.
A few months ago it was revealed that when the FBI, in the grip of J Edgar Hoover's anti-communist paranoia, asked MI5 to investigate Charlie Chaplin's background they couldn't even find out that he was born in south London.
This week "secret" documents have come to light providing an even more eye-opening insight into the world of second world war intelligence and espionage.
A psychological analysis of another legendary dodgy tache-sporter, compiled by a Cambridge academic in 1942, gave the following earth-shattering revelations. Hitler had a bit of a "messiah complex" and was paranoid about the Jews.
Suddenly it all becomes clear! If only we'd known.
Now, some might have thought that the fact that he'd established a "Thousand Year Reich" and that he'd already invaded half of Europe might have been a hint as to the former.
You don't get many self-effacing dictators - like old Etonians, being an egomaniac kind of goes with the job description.
The rabid speeches, self-aggrandising rallies and the foaming at the mouth could possibly have been clues as well.
And, oh I dunno, three-and-a-half years beforehand in 1938 a certain event known as Kristallnacht might have given at least an indication of the latter.
This could be a whole new thing - retrospective prognostication.
To make it all the more surreal, when this story broke on the wires it was strictly embargoed.
It's 70-bloody years old and Hitler's been dead since 1945. I don't think we're exactly in danger of breaching national security here.
The document was apparently found among a collection of papers belonging to the family of Mark Abrams, a social scientist who worked with the BBC's overseas propaganda analysis unit, and the psychological warfare board during the war.
Doctor Anthony said: "I could not believe it when we found this document. "I was completely shocked and I just kept reading it over and over again - it really is a fascinating piece of history."
I know the BBC has something of a reputation for being late in breaking a story, but this is ridiculous.
Written by Joseph McCurdy, the aforementioned Oxbridge academic, it refers to earlier signs of "morbid tendencies," classifying these as "shamanism," "epilepsy" and "paranoia."
I think planning extermination camps and the mass murder of homosexuals, Gypsies, Jews and communists could probably be described as "morbid." Bit harsh on epileptics though.
Intriguingly the bit the Telegraph chose to highlight was that "Hitler thought he could divine the weather."
Well so did Michael Fish but that doesn't make him a fascist.
But then the Tory party's official propaganda organ might not want to dwell on a psychological profile focusing on God complexes, paranoia and the persecution of minorities given the party's traditional leadership and policies.
The fact that it's taken 70 years for this to come to light makes one wonder what stunning revelations we have to look forward to in the years to come.
An incendiary document from 1986 saying that Thatcher may have issues when it comes to the miners and Argentina?
Coincidentally - or was it? - this week also saw the US publish a cache of documents retrieved from the Pakistan compound of Osama Bin Laden.
If anything this was even less interesting although there were a few intriguing oddities.
The most surreal was that he was apparently planning to encourage Irish Catholics, disillusioned with the church over the never ending child abuse scandals, to convert to Islam.
He'd obviously never been to a Feis.
If he knew anything about Ireland he would have approached the Free Presbyterians - half of Paisley's mob seem to think they're in the Taliban anyway.
The other bizarre item was the fact that the man who had spent decades carving a name out for himself as the world's most infamous terrorist was apparently considering re-branding al-Qaida.
What as? Just Jihad? I can't believe it's not Bin Laden?
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