The two companies fulfilled the führer's dream of German domination of grand prix racing. Their Silver Arrows won most grands prix races from 1934 onwards and set records that lasted for decades, reaching speeds of more than 186mph in 1937, and more than 250mph during land speed record runs.

Each car had a rear, three-litre engine providing 485 brake horse power. The power of some models was not equalled until the early 1980s and turbo-charged Formula One cars.

In 1937 Hitler awarded Porsche the German National Prize for Art and Science, one of the rarest decorations in the Third Reich. Ferdinand's son, Ferry, went on to develop the legendary Porsche 356.

In 1939, as war clouds gathered over Europe, Tazio Nuvolari, an Italian, drove the D-Type now up for sale to victory in the Yugoslav Grand Prix and Hermann Müller won the French Grand Prix in it.

At the end of the war the Auto Union team's cars, which are believed to have been hidden in a mineshaft in Germany, were found by the Russians who took them back to the Soviet Union so that engineers could study their technology.

Then, in the early 1970s, Paul Karassik, an American classic car collector on a visit to Poland, heard rumours that some of the fabled Auto Union Grand Prix cars were to be found behind the Iron Curtain.

Mr Karassik, who was born in Serbia but went to America and took US citizenship after the war, began a 10-year hunt for the Auto Union and other classic cars.

In 1982 he slipped away from his Intourist guide while on a trip to Russia and met a friend from Russian military school in Serbia, Oleg Tolstoy, great-grandson of the author of War and Peace.

Mr Tolstoy introduced Mr Karassik to Russian car collectors and he eventually tracked down two of the dismantled racers and smuggled them out to Florida, via Helsinki and New York, by hiding them under a false floor of a Mercedes Benz camper. Mr Karassik had the parts, but wanted the cars rebuilt. He was advised to contact Crosthwaite & Gardiner, which is based in the village of Buxted, East Sussex, and has been at the forefront of Bugatti restoration since the early 1980s.

D*** Crosthwaite, a founder-director of the firm, went to Florida and was astonished to find one complete set of Auto Union parts plus a second engine and enough original duplicate parts to rebuild the two cars manufactured originally in 1938 and 1939.

One was sold to Audi. The other car, the winner of the Reims and Belgrade Grand Prix, was bought by Abba Kogan, a Brazilian collector who lives in Monaco.

It is Mr Kogan's car that is being sold.

A spokesman for Christie's in Paris, said: "The 1939 Auto Union could well break the record. It is more important that the Bugatti Royale, which is a fantastic car, but the Auto Union has everything.

"It is the last, fastest and most modern version of that model and the story not just of its grand prix wins in 1939 but the whole history of its rescue and restoration makes it truly unique."

• Auto Union's trademark symbol of four overlapping rings represented its four member companies, Horch, Audi, DKW and Wanderer. The company eventually became Audi, which retained the four-ring emblem.