Many thanks Eirikr

I will get a copy of the book.

I have read a fair bit of the BBC material and was interested in the theory put forward that the Roman 'Saxon shore forts' on the East coast served not only to defend against sea borne raiders but also as tradding posts. got me thinking that there may have been saxon populations already in place giving the initial impetus and quick teritorial gains of the initial saxon incursion. in effect they had a bridgehead and sympathetic populations.

Comparisons with the viking incursions could support this, once Danish settlements were in place in east anglia and northumbria the danes were able to expand rapidly.

just an entertainng theory