Churchill's Wizards, By Nicholas Rankin

"Oh what a tangled web we weave, when first we practice to deceive". Churchill's Wizards tells the story of Britain's deceptive operations in two world wars. At times, trying to pick the plethora of acronyms (17F, NID17, EH, A Force, SOE, ISLD, SIME, SIS, Z, MI(R), MI9, PWE), from the camouflage broth, you don't know what effect it had on the enemy, but it sure must have confused the Allies. Nicholas Rankin acknowledges this: in 1943, 40 per cent of agents in Greece were working for at least three bodies, with the attendant waste and confusion.

But despite bureaucratic overlap, once we got the hang of it, we were very good deceivers: better than the Americans, who seemed to rely only on raw firepower and numbers. Rankin traces the British love of deceptive operations in wartime – something Churchill gleefully encouraged – to the raffish adventure stories popular at the turn of the century, especially those of John Buchan.

He quotes the ever-sage George Orwell on the role that schoolboy derring-do plays in adult life: "It is probable that many people who consider themselves extremely sophisticated and 'advanced' are actually carrying through life an imaginative background which they acquired in childhood from (for instance) Sapper and Ian Hay".

In Dudley Clarke, Rankin has unearthed the last unsung hero of the Second World War. The book is replete with better-known raffish men, such as TE Lawrence and even Churchill himself, but Clarke was the acknowledged master of total deception, involving double agents, fake signals traffic, phantom forces and physical camouflage. A theatrical figure who turned his love of masquerade into a dance through the theatres of war, especially in North Africa, Clarke led a charmed life, even surviving arrest by the Spanish police while dressed as a woman.

Clarke founded A Force, the body responsible for coordinated deception, and also the Commandos. The SAS was originally one of his fakes until Lieutenant David Stirling borrowed the name for a real force. From Alamein onwards – the first great deceptive campaign, with real and dummy tank forces exchanging places overnight – to D-Day, Clarke was at the heart of the Allied push for victory.

After Clarke, hero number two for the author is the journalist Sefton Delmer, master of morale-sapping black propaganda delivered to the Germans via Aspidistra, the most powerful radio transmitter on the planet, and thousands of well-written newspapers dropped from the air. As Rankin tells it, there is an inexorable progression, a loss of innocence.

When the aeroplane entered the First World War, it was seen as a reconnaissance machine rather than a fighter, so much so that when the first British and German pilots met in the skies they saluted each other as brothers in arms – an elite, way above the troops toiling in the trenches. The salutes soon turned to hand-thrown bricks, then grenades, small-arms fire and a machine gun, synchronised to fire through the propeller without hitting it.

After Alamein, every major operation had its web of deception attached. The most striking and ghoulish such episode is "The Man Who Never Was". Before the invasion of Sicily in 1943, the Allies bluffed that Greece was to be the next target. A body was procured with family permission, an identity and a packed briefcase created. The body was floated from a submarine off the neutral Spanish coast with papers detailing the attack on Greece. Picked up by the Spanish authorities, the briefcase was eventually returned to the British. The report was read all the way up to Hitler, and Rommel was sent to Greece to deal with the attack that never came.

The narrative gathers pace from Alamein to the war's end, with deceptions matching the rising stakes. Perhaps the clinching stroke of genius was the prolongation of the D-Day deception well past the day itself. The fiction was maintained that the Normandy landings were a diversion.

For the sake of a carefully created phantom US Army, Hitler's commander Rommel kept 21 divisions in reserve for two months, by which time the Allies were unassailable. Rankin agrees with Churchill that such deceptions are necessary in wartime, but in a coda he draws the line at the intelligence justification for the 2003 invasion of Iraq. As he says, this time the deceivers were hoodwinking their own people – us.

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Peter Forbes's latest book is 'The Gecko's Foot' (Fourth Estate)