I've just been reading a book on the Vikings which ends at 1066 with the death of Harald Hardrader, but Harold Godwineson at Stamford Bridge, just before he had to scoot back south to Hasting to meet William of Normandy and be killed. William, known as the conquerer took over and so began a new phase in Englands history, I say England as Scotland, Wales and Ireland were not part of it and Great Britain didn't happen for several centuries.
England had been a part of massive Scandinavian trading networks that stetched from Dublin to Constantinople and maybe further and from the Med to Greenland and America, although they never really made much of an impact on America as far as we know. The church in Rome was trying to pull everyones eyes south again and was largely successful, although how successful if the Normans hadn't been around is unknowable.
Would we be speaking a different version of English if we had no French loan words, like pork beef and lamb, pig cow and sheep are English words and were and are sill used for the animals on the hoof, rather than on the table, which gives you some idea of the power dynamics of the time.
If Harold had won and the Harrying of the North hadn't happened would we still have what are now the ruins of the great Cistercian abbeys, such Rivelaux and Fountains? Most of Yorkshire, Derbyshire, Durham and Cumbria were more or less depopulated by Williams ethnic cleansing, leaving the north as a "desert" so sought after by the Cistercians in thier early years.
What differences can you think of and what questions do you have?