Despite our relative small size we have a huge range of accents. When Chaucer published the Canterbury Tales it was the first foray into standard English. Before that various types of English were so different they were like foreign languages. There was a story going round about merchants who went from one part of the country to another who had problems buying eggs because nobody could understand what they were saying.
The accent/use of dialect is a reminder, and the English spoken in Lincolnshire would have come from old Norse, down here it’s Anglo Saxon. In Newcastle they still call a child a bairn which is very similar to the Swedish word for child.
When I was on holiday in Crete the barman had learnt his English off a Geordie and I had to tell him that most English people don’t call kids barns, a lot don’t even know what it means.