... His new book, Ardennes 1944: Hitler’s Last Gamble is about the biggest battle on the Western Front, telling the story of the Germans’ ill-fated final stand in December, 1944.

Beevor said his revelations about how both sides killed their prisoners would be controversial.

“After the Malmedy massacre (in which 84 American prisoners of war were murdered by their German captors near Malmedy, Belgium) the Americans started to kill their prisoners, and often with the approval of commanders,” Beevor said.

“I’m not sure how the book is going to do down in the States when it comes out in November.”

He said this “blanket ancestor worshipping” of war veterans in the US had got “slightly out of control”.

Beevor’s book Berlin: The Downfall upset the Russians and he faces a five-year jail sentence if he ever visits the country again because of his accounts of Red Army soldiers raping German women.