I live in London, I can drive a little over an hour from where I live and hardly understand the people working at the petrol station. A few more hours and they start to speak French.

I have had to interpret between an Ulsterman and a South African, who were both speaking English. I think those accents have vowel shifted in opposite directions.

I was also taught a bit of Chaucer (died 1400) in English at school. Although not any of the naughty bits.

> older man approached me and spoke to me in English and I couldn’t understand a word he said

like this https://www.youtube.com/watch?v=Hs-rgvkRfwc ?