Sometimes the most influential people are the ones you cannot see. The people behind the scenes who quietly shape our futures without any widespread recognition of their influence.

The name of Juan Pujol may not be as familiar as Winston Churchill or Dwight D Eisenhower but his impact on the most important battle of the Second World War is without question.

From a small room around the corner from Hendon Central Tube station, Mr Pujol worked as a double agent and, with his army of aliases, helped to ensure the D-Day landings were a success.

A charismatic, flamboyant risk-taker known to colleagues as the greatest actor to have ever lived', Mr Pujol's story has oft circled around Hollywood, with Kevin Spacey, John Travolta and Gerard Depardieu all pencilled in to star in his biopic at one point.

"There is no doubt the work of Juan Pujol contributed to the success of the D-Day landings," explains Laurie Millner, curator of the D-Day exhibition at the Imperial War Museum.

"While obviously there were many, many people involved in its success, Pujol's work was very important indeed and cannot be ignored."

Born in Barcelona, Mr Pujol was a firm anti-fascist who first offered his services to the British consulate in 1941 but was turned down as he was deemed surplus to requirements.

Desperate to help the Allies, he turned to the Abwehr (German Military Authority) in Madrid with the intention of feeding them false information to hinder their plans. This he did, claiming to his employers that he was reporting top secret information from London, even though he was in Portugal with only an ordnance survey map, a Blue Guide To Britain' and military dictionary to hand.

"He was giving the Germans information which was false and full of errors. He was getting all his information from the most basic of sources and he managed to fool them," explains Mr Millner.

It was this kind of gung-ho spirit that would define Mr Pujol and the British soon picked up on his abilities. His reports to Madrid were of such interest to the Germans that they would be radioed across to Berlin and, in the process, intercepted by MI5 who had cracked the German's military cyphers.

Mr Pujol was flown to England and he officially joined the Allied cause, continuing to feed misinformation in the varying guises of 27 informants' to the Nazis.

From his base at 35 Crespigny Road, Hendon, he would spin elaborate lies about the positioning of Allied troops, posing as characters such as a drunken RAF officer and a Communist-hating linguist to pull the wool over the enemy's eyes. His acting skills were so good that he was given the nickname Garbo', a reference to the revered actress of the day, Greta Garbo.

To convincingly portray a Welsh fascist from Swansea and a Venezuelan living in Glasgow, he must have lived up to his moniker.

Yet his greatest performance came in the build-up to June 6, 1944 forever remembered as D-Day. He informed the top commanders of the Third Reich in advance that the Normandy landings were merely a decoy, and the major assault would be further along the coast near Calais. He also told them that large numbers of the 6th US Division had been spotted in Suffolk.

These fabrications resulted in the Germans redeploying their troops and allowing the Allied forces probably the most crucial victory of the war.

"It's quite incredible that Pujol was awarded both the Iron Cross German military honour although he never picked it up and the MBE in 1984 from the British for his efforts. Even after D-Day, the Germans did not know what he had been doing," says Mr Millner.

Indeed, it was with a certain audacity that Mr Pujol's message of acceptance of the Iron Cross offered his humble thanks' for such an honour, of which he was truly unworthy.' Mr Pujol left Britain in 1944, following a scare that he was going to be exposed as a British double agent. He eventually moved to start a new life of anonymity in Venezuela, where he lived happily until his death in 1988, aged 76.

Outside the public record office, there is little to remember him by. The current tenants at 35 Crespigny Road have never heard the name of Juan Pujol and were a little put out that strange people were knocking on their door asking questions about their home. But there is no doubting that this nondescript suburban house is a small piece of wartime history that north London can be very proud of.

Indeed it is not the only recorded incidence of wartime intelligence gathering in the borough. Churchill gave permission for the Soviet news agency Tass to set up a radio monitoring station' in a Victorian house in Oakleigh Road North, Whetstone, in 1941, allowing the Russians to gather news to broadcast back to their citizens.

Crespigny Road's own spy base could be the subject of a film soon, and Mr Pujol's story made in Hendon and built for Hollywood might finally be given the credence it deserves. Kevin Spacey as Juan Pujol? It's only a shame that the greatest actor to have ever lived' is not around to play all 28 roles himself.