Maclean's real-life exploits were entirely worthy of 007: in 1942, for example, he abducted a leading Nazi sympathiser in Persia, General Zahidi, at gunpoint from his own home and smuggled him out of the country. On another occasion he talked his way out of arrest in Italian-occupied North Africa by impersonating an Italian officer and haranguing his captors faultlessly in their own language.
So when he died last week at the age of 85, it was hardly surprising that the news reports almost unanimously described Sir Fitzroy as "the real James Bond". Yet he himself denied it, and both his own biographer and Fleming's support his denials. Frank McLynn, author of a life of Maclean, says the association of fact and fiction was natural, but almost certainly mistaken.
"Maclean was a genuine war hero. When he became well known and people realised that he and Fleming knew each other, they made the connection with Bond. But it was probably nothing more than an association of ideas."
Maclean, McLynn recalled, was not keen on the link and used to recite a list of ways in which he was unlike Bond. Most notably, the genuine hero lacked 007's obsession with clothes, brand names and gadgets, and his desire for the best of everything, from ties to revolvers.
Andrew Lycett, author of a new biography of Fleming, adds other reasons to discount the connection. Although Maclean and Fleming were friends in wartime, by the time the first Bond book, Casino Royale, was written in 1952, Fleming seems to have taken against Sir Fitzroy.
Then working for the Sunday Times, he had rejected Maclean's great book, Eastern Approaches, for serialisation in the paper, using some sharp language. The tone, Fleming wrote to the publishers, was "patronising", and the author claimed too much credit for himself, which was not in "the tradition of such books by Englishmen". That is hardly the attitude he would adopt towards the model for his hero.
But if Bond was not Maclean, who was he?
We know about the name. There was a real James Bond. He was an ornithologist and the author of The Field Guide to the Birds of the West Indies, a book which stood on Fleming's bookshelves at Goldeneye, the house in Jamaica where he wrote his novels.
This improbable source is now accepted as the likeliest inspiration for the plain, short name which to this day is a priceless trade mark for Hollywood movies and their merchandise.
But Bond the ornithologist must probably share the honour, for the name may already have been in Fleming's mind before he got to Goldeneye.
Fleming's brother, it seems, knew a Rodney Bond who was a British agent in wartime Crete (you can see that "Rodney" would not survive: imagine "The name's Bond, Rodney Bond"). Another theory has it that Fleming concocted James Bond by splicing together the names of two Eton contemporaries.
One thing we do know for certain is the face, and it was not Fitzroy Maclean, Sean Connery or Pierce Brosnan. Fleming tells us unequivocally in the novels that Bond bore a strong resemblance to Hoagy Carmichael, the American composer, singer and film actor best known for his songs Stardust and In the Cool, Cool, Cool of the Evening.
But what about the character, the action hero, the "blunt instrument", as Fleming called him, with the nerves of steel? Surely there is somebody who was the prototype of 007? Step forward Wilfred "Biffy" Dunderdale, spy extraordinaire and personal hero to Ian Fleming.
One of Fleming's earliest wartime assignments with Naval Intelligence was to visit Paris just as France was falling to the Germans in 1940, and there he met the local station chief for SIS, the overseas espionage organisation later called MI6.
If Maclean, for all his daring, was too understated to be 007, Biffy Dunderdale was not. Exquisitely dressed and a regular diner at Maxim's, he came equipped with all that was best and most expensive in life, from his Cartier cufflinks to his armoured Rolls-Royce.
He was also dashing, clever, charming and loaded with money - his family had been wealthy British merchants in Odessa, on the Black Sea. And above all, in Fleming's eyes, he was effective as a spy, having played an important role in the intelligence coup that enabled Britain to crack the German Enigma code.
But Dunderdale was not alone. Fleming also knew and admired another British agent who had a certain style, Michael Mason. Mason came from a wealthy Oxfordshire family but ran away to Canada in his youth, becoming first a fur trapper and then a professional boxer. The outbreak of the Second World War found him working as an agent in Bucharest, in still-neutral Romania, where one of his coups was to kill two Germans who had been sent to assassinate him.
They attempted to trap him in the lavatory of a railway carriage and shoot him there, but he outwitted them, broke both their necks and dumped their bodies out of the window. Perhaps significantly, something similar happens on a train in the Balkans in From Russia with Love. (In the case of Mason, the Romanians complained to the British that if their agents had to kill Germans in Romania, they should at least make an effort to hide the bodies.)
In the view of Andrew Lycett, Fleming's biographer, Bond probably owes something to both Mason and Dunderdale, and possibly also to a third man, Commander Alexander "Sandy" Glen, a former Arctic explorer who worked with Fleming in Naval Intelligence. Of all the former agents who have been linked, or have claimed to be linked, with Bond, these are the "best bets", he says.
Sandy Glen was, like Bond, a Scot and an old boy of Fettes (Tony Blair's old school), but that, Glen himself insists today, is where the resemblance ends. Now Sir Alexander Glen, after a long career in industry, he laughs off the link with 007: "I don't think it's true for a moment; I'm far too gentle, too law-abiding."
He is sure, however, that Mason and Dunderdale are part of James Bond's make-up, and he adds another, and much more important, personality: Ian Fleming himself.
"The major element in Bond's character is Ian's own self-wish," Sir Alexander said last week. "He was deskbound most of the war, and although he did a brilliant job, he certainly envied some of the death-or-glory people he was sending out."
Fleming himself said as much. "James Bond is the author's pillow fantasy," he said. "It's very much the Walter Mitty syndrome - the feverish dreams of the author of what he might have been - bang, bang, bang, kiss, kiss, that sort of stuff."
And some of the fripperies of Bond's existence - the Morland cigarettes, the vintage Bentley, the Sea Island cotton underwear - reflect Fleming's own connoisseurish tastes. This was a man, after all, who celebrated the publication of his first book by ordering from the Royal Typewriter Company a special version of its Quiet de Luxe model plated with gold.
But if Fleming admitted that Bond was wish-fulfilment in print, he also conceded that he owed something to real life. Lycett quotes the author as saying on another occasion that Bond was a "fictional mixture" of commandos and secret agents he had met during the war.
So perhaps a part of Fitzroy Maclean is in there after all - or perhaps, as Sandy Glen suggests, we are just looking at it all the wrong way around. "Maclean was an altogether more evolved character than Bond," he says. "James Bond should have wanted to be like him."