Reading your tales of Utred and the manner in which he is able to use his multi-language skill reminded me of my grandfather.
As a 14 year old he went to sea on trawlers from Lowestoft, fishing the North Sea, in those days, about 1900, the East Anglians and the Frisian Islanders were able to converse when they met at sea such was the closeness of the local vernaculars.
I have often wondered how the ancient saints got on trying to convert folk who spoke a different tongue, ie Patrick was Brithonic, some say Welsh, so how would he have managed with the Goedelic (Irish gaelic)  Were all these “tongues” a lot closer than they are today?
Most of Wales speaks what I call “open mouth Welsh”  or did, where as the North Walians speak a nasalised form and used to have a significantly different “dictionary”. I remember reading somewhere that the tribe of Cunedda was paid to moved by the Romans from the area now around Edinburgh to the Roman fort at Segontium (Caernarvon) about 350AD, so whilst the basics remained the same there were differences, do you think that this would have applied on a wider scale around the North Sea, or am I plucking at straws.
Many thanks for taking the time to read this, I hope it has not drawn you away from something more enjoyable.

Roger M Evans