the romans were the ones that founded london. They invaded britain in AD43 and not long after they founded the city of londinium. A recent dig near vauxhall that discovered evidence of a possible wooden bridge accross the thames somewhere around 3,000 years ago. It is also thought that the original city was small about the size of Hyde park. In AD60 Queen Boutica of the Iceni tribe rose up against the Romans and they fled. The city was then burned to the ground but the romans eventually got their city back. Then to protect the city they built a wall to protect the city.
The area inside of the defensive wall is known as the square mile or the city is the financial centre of the UK. there is still much evidence remaining in the city of Roman Londinium.