Much of what the public knows about the UK's Secret Service, or MI6, comes from the world of fiction - whether Ian Fleming's James Bond or John Le Carre's George Smiley.
The intertwining of fact and fiction dates back to the birth of the British intelligence service. In the early years of the 20th Century, the British public was whipped into a frenzy of "spy mania" driven by novelists and newspapers.
It was an era in which the UK was fearful of the rise of Germany and particularly its navy.
William Le Queux wrote the novel, The Invasion of 1910, which was serialised in the Daily Mail. The paper took care to adjust the invasion route the Germans were supposed to take in order to include the towns where its circulation was highest.
There was a widespread belief that the Germans were everywhere, posing as waiters and barbers, stealing secrets and preparing for war. Public pressure grew to do something and so a Secret Service Bureau was established. One half, which would become MI5, was designed to hunt for German spies. The other, which would become MI6, was to steal German secrets.
Even at that early stage, fiction was rubbing off on the real world of espionage, says Alan Judd, the biographer of Sir Mansfield Cumming, who was the first head of what became MI6.
"Le Queux knew some of the people in the War Office, I had no doubt that he had some influence on it all - certainly the culture and the climate," says Judd.
Sir Ian Fleming had experience from his time in naval intelligence
But the mythology created by fiction may have gone back even further, to the era of the Great Game - the battle between the British and Russian empires for supremacy of Central Asia, which began in the early 19th Century.
Britain had no professional spying service at the time, just the occasional gentleman amateur and soldier. But their stories were written up for the public, most dramatically in Rudyard Kipling's Kim.
These forerunners of the professional spy "did some very brave things" says Sir Colin McColl, MI6's chief between 1989 and 1994.
"And so there was a sort of general feeling that this was a good thing done by brave people. And that was followed by a whole series of authors in the first part of the 20th Century - [John] Buchan and so on. I mean terrific stuff."
Sir Mansfield Cumming was the first head of MI6
The fiction created a romanticism around spies which attracted many people to work for the service.
Among them was Daphne Park, who joined in the 1940s and rose to become a controller at MI6.
"I suppose it did start with reading [Rudyard Kipling's] Kim, reading John Buchan and reading Sapper and Bulldog Drummond and I think from a quite early age I did want to go into intelligence. I didn't know what kind or how it would be. But I always wanted it."
As well as attracting individuals to sign up for desk jobs, the daring antics of fictional spies also helped MI6 in its core work of recruiting agents - people willing to spy for the service and pass on secrets.
"There have been a lot of people with whom we've dealt across the world... [that] have come to us or worked with us because they felt we knew far more than anybody else knew," says Sir Colin.
This would be considered a poor outcome by most real-life spies
And much of the world knows MI6 though the man known as 007. James Bond's creator Ian Fleming never served in MI6 but he did work in naval intelligence during World War II and modelled Bond on a number of real life intelligence officers.
His creation - particularly once it moved to cinema - has done much to define public perceptions of MI6, although the real chief is called C not M. Egyptian intelligence services reportedly bought up copies of Fleming's books to use on their training courses.
So do people think it is like Bond?
"They usually do," says Sir Colin. "[But] no it isn't you see… we were not in the business of going out and shooting people down dark allies. That was a completely different world."
But Bond still has his uses. "Everybody watches Bond. And so why shouldn't a little bit of Bond rub off on our reputation," says Sir Colin. "If you looked at the number of people who helped us at any one time, a large number of them were Brits who were doing it for nothing - perhaps a bottle of whisky at Christmas. You know we had wonderful support and that is hugely valuable... based on the reputation."
However, Fleming's character seems to have made less of an impression on the Russians, according to former KGB colonel Mikhail Lyubimov.
This would not be considered best practice for secretaries in the real MI6
"Bond was never considered to be a serious film in the KGB," says Mr Lyubimov, curtly.
The other figure who has done much to shape the public understanding of MI6 is John le Carre. The portrayal of often flawed characters draws a mixed reception from real life spies.
"I mean there were two feelings I think in the service over the years," explains Sir Colin McColl. "There were those who were furious with John Le Carre because he depicts everybody as such disagreeable characters and they are always plotting against each other and so on… So people got rather cross about that.
"But I thought it was terrific because, again, it carried the name that had been provided by Bond and John Buchan and everybody else, it gave us another couple of generations of being in some way special."
Ms Park, it's fair to say, is not a fan.
"He dares to say that it is a world of cold betrayal. It's not. It's a world of trust. You can't run an agent without trust on both sides." Le Carre, who served briefly in MI5 and MI6, declined to be interviewed.
As the British Secret Service has come out of the shadows, some of the myth and mystery has certainly disappeared. Some insiders believe this is inevitable and for the best, laying to rest some of the crazier ideas about the world of MI6.
But there are a few, all the same, who may rather miss it.