In 43 C.E., Romans built a bridge over the Thames. The bridge was likely a wooden drawbridge with stone supports. Thus was the town born. Because of the river's inlandaccess, the Romans made it an important port. By 193 C.E., London was thriving under the Romans, and a wall was built around the city.

After Rome abandoned Britain, the people of London were able to protect their town, thanks to the city wall. The Anglo-Saxon Chronicle records: in 456, after a defeat at Crayford in Kent, "the British fled with great haste to London." The Anglo-Saxons did not move into London proper until after the sixth century-- and when they did, the evidence indicates that they shared the town with the British natives.