Whenever the British Press wants to attack the Royal Family, they make a jibe about "their foreign roots". The Royals – as they say – are simply a posh version of German invaders. But did German relatives really influence decisions made by any British monarchs or are they just an "imagined community", invented by journalists and historians?

The Royal Archives at Windsor gave the authors – among others John Röhl, doyen of 19th century monarchical history – open access to Royal correspondences with six German houses: Hanover, Prussia, Mecklenburg, Coburg, Hesse and Battenberg.