Early Franco Prussian War. I can actually see the British telling the French to fuckoff because the balance of power in Europe is pretty good right now, especially with both Germany and the Polish-Lithuanian Commonwealth to stave off Russia. Germany is not trying to challenge Britain at sea, and the Italian peninsula is unified as the New Roman Empire. From their political perception, its France that is being the balance upsetter, acting like a convulsing tantrum prone child because Germany has finally grown up, and chucked them out for the first time in a long time.