When the Romans left the country quickly reverted to its former tribal state with a total population little more than one of our cities today. It would not be true to say that the Saxons invaded, they simply moved in over a long period of time. Slepe, was little more than a tiny hamlet on what was then the edge of the Great Fen. The village grew up at this point because it was one of the crossing places on the river Great Ouse. It was given the name Slepe, Anglo-Saxon for "muddy" for obvious reasons, there were no bridges here at that time you had to wade through the river.
The small hamlet grew to become a village. It was not a bad place to live as standards went in those days, good transport with roads and the river which also provided plenty of fish. It was surrounded by dense forest the habitat of plentiful game and also a place the local inhabitants could run away to during times of unrest. The peaty soil was just the thing for growing crops as it still is.
So on the whole if you had to be a 'villien' or 'surf' (peasant) then Slepe was not a bad place to be. Over time the inhabitants built a small church and some of them became quite wealthy. One wealthy family in particular ending up owning most of land. This was to become the first milestone in the history of St. Ives.