The darling English language
The idiosyncratic trait which has made English a global language involves its treatment of vowels. When, sometime around 1,000 BC, Old English speakers changed their treatment of vowels, they produced "a dramatic reduction in the number of distinct endings (inflections) that could be added to words. . ." (Stephen Oppenheimer explains this and much more in The Origins of the British, 2007.)
Reducing the number of distinct endings meant it was easier to learn English – you did not have to add a different ending to every word depending on its role in a sentence. It also meant that English became a language that welcomed foreign words.
The British people were brilliant travellers, and that's one of the reasons the English language spread. But English is also hospitable. English accepted contributions from Ancient Greek, Latin, French, Gaelic, Norse, German, Indian, Chinese, Japanese, etc, while retaining a unique down-to-earth spirit with Old English words - love, friend, free, fair, darling, joy, heart, son, daughter, husband, wife, clothes, hair, bed, wonderful, word, wise, evening, day, wood, field, hill, beach, house, song, storm, tree, truth, sun, light, food, holiday, game. . . English has been incredibly successful, but between the 11th and 13th centuries it wasn't clear the English language was going to survive in England.
The French and Latin-speaking Norman invaders almost wiped it out. For more than one hundred years books were not written in English, but the English spoke English, insisted on speaking English, fought to speak English.
Listening to Eric Clapton, we're glad they did.