His passion for the operas of Richard Wagner is well known. Now it can be revealed that Hitler planned the invasion of Poland with the help of an atlas borrowed from the German composer’s grandson.

The Fuhrer turned to the Wagner family for assistance during one of his regular visits to the annual Bayreuth music festival in the summer of 1938.

Hitler wanted to illustrate his plans for a possible Polish invasion while in discussion with some of his henchmen.

“He just asked for a geography map and we found one which was my my brother’s,” recalled Friedelind Wagner, the composer’s granddaughter. Her brother, Wolfgang, was a teenager at the time.

Friedelind went on to explain how Hitler drew a series of lines on the map to show potential German troop movements. The invasion of Poland took place a year later, and last week its 70th anniversary was commemorated.

Unlike most of her family, Friedlin was not sympathetic to the Nazi cause and fled to America during the Second World War.

She was interviewed by Tony Palmer, a British documentary film-maker, before her death in 1991. Her recollections will be broadcast for the first time next Sunday (Sep 13) on ITV1 as part of a South Bank Show special on the Wagner family.

“People knew that Hitler was a huge fan of Richard Wagner’s music and so they were not surprised that he would go to the (Bayreuth) festival,” said Palmer, who has uncovered footage of the Fuhrer at the event.

“But what most did not realise was that he also used Bayreuth regularly as camouflage. In other words, people thought he was there for the music but in fact he was there as much, out of the public eye, to plot Nazi expansion plans.”

While in Bayreuth Hitler stayed in a house owned by Wagner family.

Next weekend’s programme also shows how the Fuhrer was romantically linked to an English woman. The object of his desire was Winifred Williams, an orphan from Hastings, who was adopted by a musical family in Germany and later married off to Siegfried Wagner, one of the composer’s sons.

Hitler got to know Winifred in the late 1920s during his trips to Bayreuth. The couple fell in love and there was serious talk of Winifred divorcing her husband, who was gay. However, Hitler, as “a good Catholic”, felt he could not be seen to break up the marriage.

The South Bank Show special on the Wagner Family is on ITV1 on Sunday, September 13 at 10.15pm