As definitions of density vary, getting reliable comparative data can be difficult. Comparing cities’ density is further complicated by the different definitions of, and boundaries for, a city. For example, some cities’ administrative boundaries have a substantial undeveloped hinterland which significantly reduces the average density even if the core, which most would regard as the true city, is very highly developed. Accordingly, London’s density ranking compared to other cities depends in part on the definitions of the area studied.

The GLA’s boundary accommodates 55 people per hectare on average, a total of 8.6 million people in 3.4 million homes⁵. In inner London⁶ this figure is 101 people per hectare, which equates to 37 per cent of the population (3.2 million people) in just 20 per cent of London’s total land area. While densities in inner London are high compared to the Greater London average, they are not high compared to other city centres⁷. For example, the Department de Paris has a population of 2.2 million people and a population density of 213 people per hectare. Madrid’s Centro district has a population of 150,000 people, which works out at 286 people per hectare. This is almost double the population density of London’s densest boroughs such as Islington, which has a population of 200,000 at 138 people per hectare, and Kensington and Chelsea which has a population of 159,000 people at 130 people per hectare.

Central Paris is seen as one of the most desirable locations in the world, characterised by its mid-rise mansion blocks along grand tree-lined Haussmannian boulevards. Likewise, Centro Madrid is exemplified by mid-rise mansion blocks and quality streetscapes that support its vibrant cafe culture. Both examples show that higher density does not have to mean high-rise and the way in which a place is designed is more important to its desirability than the measurement of its density.

Current land use in London

Figure 4 looks at how London’s 157,000 hectares of land is utilised. It shows that the highest proportions of land are taken not by buildings but by green space and domestic gardens: 62% overall⁸. This proportion is higher in the outer boroughs: more than half of all land in Havering and Bromley is green space while about a third of all land in Sutton, Harrow and Croydon is domestic gardens. The interaction between London’s green space and the built environment is what gives much of the city its character. Even in the densest boroughs, there is still considerable green space. In Kensington and Chelsea, high density but well-designed mid-rise 19th century mansion blocks are interspersed by garden squares and parks which provide space and light. Measured density and perceived density are not necessarily aligned.

The challenge for London is to make better use of its brownfield land while enhancing the city’s urban fabric and green spaces that define the character of the capital. Higher densities can be accommodated by different building forms and do not rely solely on high-rise development – a point that is discussed further in the next section.

5. Census 2011
6. Office of National Statistics definition of inner London (Hackney, Kensington and Chelsea, Islington, City of London, Hammersmith and Fulham, Wandsworth, Tower Hamlets, Haringey, Camden, Lambeth, Southwark, Westminster, Lewisham and Newham).
7. World and London, Savills: 2015.
^{8. Generalised Land Use Database Office of National Statistics 2005.}