With the Romans on the descent by then what type of logistics would have helped them fight their way out of there?
I’d long thought they’d left fragmentarily.
“Time to head home, boys,” the Legion commander says. Though I bet a lot of ‘em went AWOL and stayed.
Actually, no. They left when the Roman governor of Britain decided that he should be Emperor, and he took the Legions with him. After his rebellion was defeated, the Legions were never replaced.
That left the coasts clear (literally) for the Saxon pirates to raid at will. One of the local British kings invited a Saxon chief to take over the defense of his kingdom in return for land. The Saxons then just moved in and took over.