Tldr. 1066 French didn't have them. Later on that each language French / English independently solved the "need more letters" problem. English adds them e.g. "t

Tldr. 1066 French didn't have them. Later on that each language French / English independently solved the "need more letters" problem. English adds them e.g. "th" is 2 letters for a sound. French uses diacritics.