Discussing the plot by British-led mercenaries to overthrow him, President Obiang Nguema of Equatorial Guinea made an important cultural point: “Simon Mann was used as an instrument but there were material and intellectual authors behind it.”

Those authors can now be named. They are Graham Greene, George MacDonald Fraser, Daniel Carney (author of The Wild Geese) and, above all, the undisputed doyen of mercenary fiction, Frederick Forsyth.

Spies read John le Carré, lawyers read Rumpole, private detectives read Sherlock Holmes and policemen read Ian Rankin and Colin Dexter; but no profession is so entirely entranced by and indebted to its own fiction as that of the mercenary. Mercenaries believe their own mythology, and so do we.

The ludicrous abortive coup launched by Mann and his men in 2004 is possibly the only event in world history to follow, almost page for page, the plot of an airport thriller, forging an odd - and inadvertently hilarious - intermingling of fact and fiction. You couldn't make it up, because someone already has.

In the early 1970s, Forsyth began researching The Dogs of War by infiltrating the seamy world of mercenaries. Forsyth has said that he does not know whether the plot of the resulting novel, depicting a coup in a small, mineral-rich African state, was inspired by something that the mercenaries said, or whether his own half-formed ideas prompted what happened next.

Either way, in 1973, a soldier of fortune named Alexander Gay loaded a boat with mercenaries and headed for Equatorial Guinea intending to topple the Government, a plan that was foiled when the invaders were intercepted in the Canary Islands after a tip-off from the British Embassy in Madrid.

The next year Forsyth published his fictional version, in which a British tycoon hires a bunch of mercenaries to overthrow the government of the fictional republic of Zangora after it is found to be sitting on a fortune in platinum. Art imitating life, which may have been inspired by art.

Thirty years later it was life's turn to mimic art again. The coup attempt against President Obiang may have been aimed at soaking Equatorial Guinea's oil reserves, and the cost of black market weaponry has certainly gone up in the intervening years, but in most other respects the plot was a faithful replica of the one that Forsyth invented.

The alleged plotters even speak like characters in a novel, referring to one another as “Scratcher”, “Smelly” and “the Cardinal”, and drooling over the “large splodges of wonga” involved.

“Knocking off a bank or an armoured truck is merely crude. Knocking off an entire republic has, I think, a certain style.” So says the chief coup-plotter in The Dogs of War, but the remark could just as easily have come from the lips of Mann - an Old Etonian, the son of a former England cricket captain, heir to a brewery fortune and a bespectacled adventurer, a character whom Forsyth himself would have rejected as too improbable for fiction.

Even the court authorities appear to be having difficulty separating invention and reality. Court papers specifically referred to Mann's alleged co-conspirator, Nick du Toit, now serving 34 years in a Malabo jail, as a “dog of war”. After an earlier coup attempt involving army officers in 1988, one soldier was apparently found guilty of plotting simply on the basis that he owned a copy of the novel.

To cap it all, Mann is said to have started writing his own book on scraps of paper smuggled into his cell. Will it be fiction or nonfiction?

I suspect that Mann himself may no longer be aware of the difference.

The British public has a longstanding affection for dogs of war, partly because Britain has bred so many of this peculiar species in both history and literature. From Sir Francis Drake to Harry Flashman, we applaud the swashbuckling freelance fighter, the soldier of fortune, ready to sell his sword to the highest bidder, install a new potentate and make a splodge of wonga at the same time.

Mercenaries see themselves as kingmakers, but many would also be kings. “We are going away to be kings,” Daniel Dravot declares in Rudyard Kipling's The Man Who Would Be King. “In any place where they fight, a man who knows how to drill men can always be king.”

We call them freebooters, adventurers, privateers or knights errant - in occupied Iraq, they are called “contractors in the peace and security industry” - but no euphemism can disguise that mercenaries are hired killers, and often dangerous fantasists, drunk on their own deluded self-image.

Simon Mann may seem like a picaresque throwback to an earlier age, but in reality, private guns are available for hire today as never before. According to Jeremy Scahill, the author of a book about Blackwater Worldwide, the private US military company whose personnel shot dead at least 17 Iraqi civilians in one incident last September: “CIA type services, special operations, covert actions and small scale military and paramilitary forces are now on the world market in way not seen in modern history.”

There are more private contractors than American soldiers in Iraq.

Mann and his motley mercenaries, however, fit precisely into the traditional fictional image of the British freebooter: seedy and greedy, tough and arrogant. Even as he faces jail, Mann cannot resist playing his allotted part, with irony: “I am like a coiled spring,” he told reporters, “ready to bounce into action.”

The very familiarity of that role, the farcical plot, the blurring of myth and reality, have all helped to obscure another, parallel narrative, just as recognisable but far more important. This is a story that might have come from the pen of Joseph Conrad, Evelyn Waugh or Giles Foden, the author of The Last King of Scotland. It is the story of a ruined African state, repressive, brutal and corrupt.

Equatorial Guinea could be rich and stable. Instead, it is a sore in the armpit of Africa, its three million inhabitants cowed and poverty-stricken, its oil riches distributed among the President's cronies.

The trial has enabled a Machiavellian despot to twist the story to his own advantage, to pose as the victim of violent interference by white terrorists bent on undermining an independent African regime. No one will be enjoying the spectacle taking place in the Malabo courtroom more than President Robert Mugabe of Zimbabwe.

Instead of ousting a tyrannical regime, Mann and his men have strengthened it.

For this is the other aspect of mercenary action that fiction often ignores: it doesn't work. Outside the pages of paperbacks, mercenary coups almost inevitably fail. Machiavelli himself gave warning: “If anyone supports his state by the arms of mercenaries, he will never stand firm or sure”, a truth that America has discovered as it tries to wage an increasingly privatised war in Iraq.

Mercenaries make fine fiction, but they do not make kings, peace, or splodges of wonga. Instead, dogs of war create havoc and leave a filthy mess for others to clear up.

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