Mostly looking for a cultural divide, not necessarily a date
There isn't a separation. English is just the modern way of saying Anglisc. A better question is when the Saxons and Jutes ceased to consider themselves as independent from the Angles.
hi! there have been a few discussions on this that could be helpful; I've found two, but I'm sure there were more, so if anyone can remember, please reply with links - thx!