They were only 3ft tall but what the regiments of dummy paratroopers, dropped over Normandy on D-Day, lacked in stature they more than made up in their ability to confuse the enemy.

Some 500 of the dummies, nicknamed “Ruperts” after army slang for an officer, were dropped behind German lines. They were designed to burst into flames when they hit the ground, diverting the Germans from the real landings and creating the impression a fierce battle was raging.

Now one of the rare surviving Ruperts is expected to fetch up to £1,000 when it is sold at auction this Thursday.

They were dropped in four locations over Normandy at the same time thousands of Allied paratroops landed elsewhere on the night of June 5, 1944. They were accompanied by six SAS soldiers who had the job of playing loud recordings of gun and artillery fire.

The deception, known as “Operation Titanic” was a magnificent success, although four of the six SAS men were captured and spent the rest of the war in German prison camps.

The Ruperts were half the height of a real soldier and made from hessian sacking stuffed with rags, straw and other flammable materials. But when they were dropped at night from Stirling, Halifax and Hudson bombers they were sufficiently realistic to convince the Germans they were under attack from all directions.

The operation was portrayed in the film The Longest Day which mistakenly portrayed the dummies as lifesize rubber mannequins.

The Rupert coming up for auction did not ignite on landing and was later recovered by a French local who spent years collecting D-Day-related items before setting up his own museum. It has been in his ownership ever since and is in excellent condition with a fully functioning parachute. Ernst-Ludwig Wagner, from the Hermann Historica auctions in Munich which is selling the paradummy, said: “These are quite rare and this example came from a museum in Normandy in France. Other leftover paradummies are on display in British museums but this one was used, as it has come from France.

“During Operation Titanic hundreds of paradummies were dropped and there are very few left, simply because they were designed to burn on landing.” During the operation, the Americans dropped their own dummies nicknamed Oscars.

Dummy paratroopers were also used by the Germans, who dropped similar decoys during the Battle of the Netherlands in 1940.

They were used throughout the war by both sides and more recently were used during the Vietnam war and in Iraq and Afghanistan.