Innermost part of London, England
Source (Wikipedia): Central London

Central London is the innermost part of London, in England, spanning the City of London and several boroughs. Over time, a number of definitions have been used to define the scope of Central London for statistics, urban planning and local government. Its characteristics are understood to include a high-density built environment, high land values, an elevated daytime population and a concentration of regionally, nationally and internationally significant organisations and facilities.