City of London four of the eight wards accounted for 67% of the 'square mile' and held 86% of the population, and these were in fact similar to and named after four City of London wards: The City has a unique electoral system. Most of its voters are representatives of businesses and other bodies that occupy premises in the City. Its ancient wards have very unequal numbers of voters. In elections, both the businesses based in the City and the residents of the City vote. The City of London Corporation was not reformed by the Municipal Corporations Act 1835, because it had a
City of London Bridge, Tower Bridge and the Millennium Bridge. The City's flag flies over Tower Bridge, although neither footing is in the City. The size of the City was constrained by a defensive perimeter wall, known as London Wall, which was built by the Romans in the late 2nd century to protect their strategic port city. However the boundaries of the City of London no longer coincide with the old city wall, as the City expanded its jurisdiction slightly over time. During the medieval era, the City's jurisdiction expanded westwards, crossing the historic western border of the original settlement—the River Fleet—along Fleet