Queen Nazi Salute
Queen Elizabeth filmed performing Nazi salute as young girl Sun

Buckingham Palace faces further embarrassment following the Queen Nazi salute controversy with a Channel 4 documentary due to be aired later this month.

Prince Philip: The Plot to Make a King will expose the Duke's German connections and reveal the unpublished memoirs of one of his sisters, Sophie, in which she describes her admiration for Hitler calling him "charming" and a seemingly modest man".

Her husband would later become an SS colonel and head of one of the Nazi intelligence agencies explaining the difficulties and backlash Philip faced from the Royal family and government before marrying Elizabeth. His other two sisters also married senior Nazi officers.

It follows the recent ridicule the Queen has faced for appearing in footage as a six or seven-year-old girl performing a Nazi salute alongside her sister Princess Margaret, the Queen Mother and being encouraged by her uncle, the future king Edward VIII.

Although it is obvious the Queen at the age would be have unaware of the meaning of the salute – it has brought into question the Royal family's links to the Third Reich before the Second World War.

Mark Almond, a professor of modern history at Oxford University, told The Guardian: "Opening up aspects of the Queen's early years is not going to damage respect for the monarchy. It can only reinforce her standing with the public.

"This film reminds us of how many challenges this country has overcome in the last eight decades under the Windsors."

But one commentator has said the family who were playing in the grounds of Balmoral were merely waving to someone out of the frame.

According to the Daily Express, the Queen mother said: "Oh look darlings, there she is!"

To which Prince Edward replies: "Yes, yes, come on, come on, give her a wave."

Then Princess Elizabeth says to Prince Margaret: "Wave! Wave! Hellooooo."

Jessica Rees, who was born deaf, and is the country's leading forensic lip reader for organisations including the Met Police and the FBI, said: "I viewed this footage 23 times, and I am in no doubt about what they are saying to each other. This has nothing whatsoever to do with any Nazi salute. Anyone who says the contrary is simply wrong."

The footage was submitted to The Sun and may have been accidentally leaked by Buckingham Palace.

The palace has launched an official investigation and has not ruled out taking legal action after the Queen was said to be angry about the release of the video and the suggestions her family were Nazi sympathisers.

"The Queen was devoted to her mother and knows she, more than anyone, despised Hitler and inspired Britain to stand firm against the Nazis," a royal source told The Mirror.

"She wants to know who leaked this film, how they got it, but most of all why they did it."