Greater London Built-up Area

From the longer Wikipedia page

The Greater London Built-up Area, or Greater London Urban Area, is a conurbation in south-east England that constitutes the continuous urban area of London, and includes surrounding adjacent urban towns as defined by the Office for National Statistics. It is the largest urban area in the United Kingdom with a population of 9,787,426 in 2011.

The Greater London Built-up or Urban Area had a population of 9,787,426 and occupied an area of 1,737.9 square kilometres (671.0 sq mi) at the time of the 2011 census.

It includes most of the London region – omitting most of its woodland, small, buffered districts, the Lee Valley Park, and the two largest sewage treatment works serving London by the River Thames. Outside the region's administrative boundary, it includes contiguous suburban settlements and a few densely populated outliers connected to it by ribbon development. Its outer boundary is constrained by the Metropolitan Green Belt and it is therefore much smaller than the wider metropolitan area of London.