How would planting the German flag offend the Brits? The Brits used to be allies and friends with some of the German monarchs. It wasn't until WW1 when they became hostile towards each other. In the Revolution, the Germans sent mercenaries to help fight alongside the Brits and again during the Napoleonic Wars.
On top of that, the English are part German, because of all the Germanic Saxons who immigrated there, along with the Anglos. Heck, even the British Monarchy has some German blood in them.
The French have a rivalry with the British that goes back centuries, hence the reason I suggested Napoleon.